NORTHERN ILLINOIS GAS CO /IL/ /NEW/
10-Q, 1997-11-13
NATURAL GAS TRANSMISSION
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                               UNITED STATES
                     SECURITIES AND EXCHANGE COMMISSION
                          Washington, D.C.  20549
                                 FORM 10-Q



(Mark One)
      
[ X ] Quarterly Report Pursuant to Section 13 or 15(d) of the Securities
      Exchange Act of 1934
        For the quarterly period ended September 30, 1997

                        or

[   ]   Transition Report Pursuant to Section 13 or 15(d) of the Securities
        Exchange Act of 1934
        For the transition period from            to            

Commission file number 1-7296



                         NORTHERN ILLINOIS GAS COMPANY
                         (Doing business as Nicor Gas)            
             (Exact name of registrant as specified in its charter)
        
                Illinois                               36-2863847    
        (State of incorporation)                   (I.R.S. Employer
                                                  Identification No.)

            1844 Ferry Road                                       
          Naperville, Illinois                         60563-9600    
         (Address of principal                         (Zip Code)            
          executive offices)
        
 
                              (630) 983-8888          
                       (Registrant's telephone number)


Registrant meets the conditions set forth in General Instruction H(1)(a) and
(b) of Form 10-Q and is therefore filing this Form with a reduced disclosure
format.

Indicate by check mark whether the registrant (1) has filed all reports
required to be filed by Section 13 or 15(d) of the Securities Exchange Act
of 1934 during the preceding 12 months and (2) has been subject to such
filing requirements for the past 90 days.  Yes [X] No [ ]
 
Shares of common stock, par value $5, outstanding at October 31, 1997, were 
15,232,414, all of which are owned by Nicor Inc.



                                                                            
Nicor Gas                                                            Page i 

Table of Contents

                                                                       Page
Part I.      Financial Information                                     
Item 1.      Financial Statements (Unaudited)                            1

             Consolidated Statement of Income -                          
               Three, Nine and Twelve Months Ended
               September 30, 1997 and 1996                               2

             Consolidated Statement of Cash Flows -                      
               Nine and Twelve Months Ended
               September 30, 1997 and 1996                               3

             Consolidated Balance Sheet -                                
               September 30, 1997 and 1996, and 
               December 31, 1996                                         4

             Notes to the Consolidated Financial Statements              5

Item 2.      Management's Discussion and Analysis of                     
               Financial Condition and Results of 
               Operations                                                7

Part II.     Other Information

Item 1.      Legal Proceedings                                          10

Item 6.      Exhibits and Reports on Form 8-K                           10

             Signature                                                  11

             Exhibit Index                                              12




Selected terms:

Ill.C.C. - Illinois Commerce Commission.

Mcf, Bcf - Thousand cubic feet, billion cubic feet.
             
Degree days - The extent to which the daily average
              temperature falls below 65 degrees
              Fahrenheit.

              


Nicor Gas                                                            Page 1 



As part of Nicor's plans to bring all of its energy-related businesses
together under one name, Northern Illinois Gas Company will be doing
business as Nicor Gas.  Although Northern Illinois Gas will continue to
function as a legal entity, products and services are now marketed under a
single common brand identity "Nicor."  Northern Illinois Gas is hereinafter
referred to as Nicor Gas.


PART I - Financial Information

Item 1.  Financial Statements

         The following condensed unaudited financial statements of Nicor Gas
         have been prepared by the company pursuant to the rules and
         regulations of the Securities and Exchange Commission (SEC). 
         Certain information and footnote disclosures normally included in
         financial statements prepared in accordance with generally accepted
         accounting principles have been condensed or omitted pursuant to
         SEC rules and regulations.  The condensed financial statements
         should be read in conjunction with the financial statements and the
         notes thereto included in the company's latest Annual Report on
         Form 10-K.

         The information furnished reflects, in the opinion of the company,
         all adjustments (consisting only of normal recurring adjustments)
         necessary for a fair statement of the results for the interim
         periods presented.  Because of seasonal and other factors, the
         results for the interim periods presented are not necessarily
         indicative of the results to be expected for the full fiscal year.

 


<TABLE>
Nicor Gas                                                                                            Page 2 

Consolidated Statement of Income (Unaudited)
(Millions)
<CAPTION>
                                        Three months ended       Nine months ended       Twelve months ended
                                           September 30             September 30             September 30   
                                         1997       1996          1997       1996          1997       1996  

<S>                                    <C>        <C>           <C>        <C>           <C>        <C>
Operating revenues                     $  151.1   $  161.0      $1,215.1   $1,098.3      $1,727.0   $1,515.2

Operating expenses
  Cost of gas                              55.7       68.6         778.0      664.9       1,122.0      924.7  
  Operating and maintenance                35.1       36.0         109.7      113.2         153.1      157.5
  Depreciation                             13.2       13.0          81.3       77.4         115.7      107.4
  Taxes, other than income taxes           12.0       11.6          94.7       87.5         124.6      113.1 
  Income taxes                              9.1        7.7          44.3       45.6          61.8       62.9
                                          125.1      136.9       1,108.0      988.6       1,577.2    1,365.6

Operating income                           26.0       24.1         107.1      109.7         149.8      149.6

Other income (expense)
  Interest income                            .6          -           1.4         .1           1.4         .1
  Other, net                                 .2          -            .6         .6           1.9        1.2
  Income taxes on other income              (.3)         -           (.7)       (.2)          (.9)       (.3)
                                             .5          -           1.3         .5           2.4        1.0

Interest expense
  Interest on debt, net of
    amounts capitalized                    10.6       11.2          33.0       31.4          46.1       41.6
  Other                                      .3         .1            .9        2.4            .9        2.9
                                           10.9       11.3          33.9       33.8          47.0       44.5

Net income                                 15.6       12.8          74.5       76.4         105.2      106.1
  
Dividends on preferred stock                 .1         .1            .4         .4            .5         .5

Earnings applicable to common stock    $   15.5   $   12.7      $   74.1   $   76.0      $  104.7   $  105.6


<F1>
Nicor Gas is a wholly owned subsidiary of Nicor Inc.  Earnings and dividends per share
information is therefore omitted.

<F2>   
The accompanying notes are an integral part of this statement.
</TABLE>


<TABLE>
Nicor Gas                                                                                            Page 3 

Consolidated Statement of Cash Flows (Unaudited)
(Millions)
<CAPTION>
                                                                 Nine months ended       Twelve months ended
                                                                    September 30             September 30   
                                                                  1997        1996         1997        1996 
Operating activities
  <S>                                                           <C>         <C>          <C>         <C>
  Net income                                                    $  74.5     $  76.4      $ 105.2     $ 106.1
  Adjustments to reconcile net income to net 
    cash flow provided from operating activities:
      Depreciation                                                 81.3        77.4        115.7       107.4
      Deferred income tax expense (benefit)                         3.7        (1.6)         4.3          .8  
      Change in working capital items and other:
        Accounts receivable, less allowances                      175.3       123.7         (9.2)      (40.4)
        Gas in storage                                            (27.0)      (72.0)       (10.2)      (76.1)
        Deferred/accrued gas costs                                 61.7       (33.7)        53.0       (25.2)
        Accounts payable                                          (56.6)      (74.7)        28.6       (26.2)
        Accrued interest                                           (5.0)      (11.9)         1.4        (4.2)
        Other                                                      (9.0)      (27.7)         (.2)      (28.6)
  
  Net cash flow provided from operating activities                298.9        55.9        288.6        13.6

Investing activities
  Capital expenditures                                            (65.7)      (68.2)      (105.2)     (116.3)
  Other                                                             1.8         (.7)         4.4         (.7)

  Net cash flow used for investing activities                     (63.9)      (68.9)      (100.8)     (117.0)
   
Financing activities
  Net proceeds from issuing long-term debt                         49.7        74.3         49.7       123.8
  Disbursements to retire long-term debt                          (25.0)      (50.0)       (25.0)      (50.0)
  Short-term borrowings (repayments), net                        (176.1)       56.4        (99.9)      114.4
  Dividends paid                                                  (83.8)      (67.3)      (108.3)      (84.5)
  Other                                                             (.5)        (.4)         (.6)        (.4)
  
  Net cash flow provided from (used for) financing
    activities                                                   (235.7)       13.0       (184.1)      103.3

Net increase (decrease) in cash and cash equivalents                (.7)          -          3.7         (.1)

Cash and cash equivalents, beginning of period                      4.4           -            -          .1

Cash and cash equivalents, end of period                        $   3.7     $     -      $   3.7     $     -

Supplemental information
  Income taxes paid, net of refunds                             $  35.6     $  49.5      $  53.0     $  57.5
  Interest paid, net of amounts capitalized                        38.4        46.6         44.9        49.3


<F1>
The accompanying notes are an integral part of this statement.
</TABLE>
 


<TABLE>
Nicor Gas                                                                                            Page 4 

Consolidated Balance Sheet (Unaudited)
(Millions)
<CAPTION>
                                                           September 30       December 31       September 30
                          Assets                               1997               1996              1996    

<S>                                                          <C>               <C>                <C>
Gas distribution plant, at cost                              $ 2,999.6         $ 2,942.8          $ 2,911.9 
  Less accumulated depreciation                                1,355.0           1,280.9            1,253.4

                                                               1,644.6           1,661.9            1,658.5
Other property and investments, net of accumulated
  depletion of $14.5, $14.5 and $34.4, respectively                6.8               8.8                8.5        
                                                                
                                                                                   
Current assets
  Cash and cash equivalents                                        3.7               4.4                  -
  Accounts receivable, less allowances of $7.5,   
    $6.1 and $5.4, respectively                                  128.3             303.6              119.1  
  Gas in storage, at last-in, first-out cost                     145.2             118.2              135.0
  Deferred gas costs                                                 -              51.1               42.4
  Other                                                           23.5              28.2               23.1  

                                                                 300.7             505.5              319.6

Other assets                                                      77.1              69.0               68.4

                                                             $ 2,029.2         $ 2,245.2          $ 2,055.0

               Capitalization and Liabilities

Capitalization                                             
  Long-term debt                                             $   520.9         $   495.5          $   495.9
  Preferred stock
    Redeemable                                                     8.1               8.6                8.6
    Nonredeemable                                                  1.4               1.4                1.4
  Common equity                                               
    Common stock                                                  76.2              76.1               76.2
    Paid-in capital                                              107.9             107.9              107.9
    Retained earnings                                            496.6             498.4              500.6

                                                               1,211.1           1,187.9            1,190.6
Current liabilities
  Long-term obligations due within one year                       25.5              25.5               25.5
  Short-term borrowings                                          108.1             284.2              208.0
  Accounts payable                                               234.9             291.5              206.3
  Accrued interest                                                26.9              31.9               25.5
  Other                                                           48.5              50.7               30.0

                                                                 443.9             683.8              495.3
Deferred credits and other liabilities
  Deferred income taxes                                          181.0             179.5              173.2
  Regulatory income tax liability                                 82.1              83.8               84.5
  Unamortized investment tax credits                              46.8              48.4               49.2
  Other                                                           64.3              61.8               62.2

                                                                 374.2             373.5              369.1

                                                             $ 2,029.2         $ 2,245.2          $ 2,055.0   


<F1>
The accompanying notes are an integral part of this statement.             
</TABLE>
 



Nicor Gas                                                            Page 5 

Notes to the Consolidated Financial Statements (Unaudited)

ACCOUNTING POLICIES

Depreciation is calculated using a straight-line method for the calendar
year.  For interim periods, depreciation is allocated based on gas
deliveries.  In April 1996, the composite depreciation rate was increased to
4.1 percent from 3.7 percent.

RATE PROCEEDING

On April 3, 1996, the Ill.C.C. granted Nicor Gas a $33.7 million general
rate increase, of which $12 million relates to a change in the company's
composite depreciation rate.  The new rate structure, effective April 11,
1996, allows Nicor Gas to recover a larger proportion of its fixed costs
during warmer months.  In June 1997, the order was upheld by the Third
District Appellate Court of Illinois.

LONG-TERM DEBT

In October 1997, Nicor Gas issued $50 million of 7-3/8% First Mortgage Bonds
due in 2027.  The net proceeds from the sale of the bonds will be used,
together with other corporate funds, for the November 1997 retirement of $50
million of 9% First Mortgage Bonds due in 2019.

In June 1997, Nicor Gas sold $50 million of 6.75% First Mortgage Bonds due
in 2002.  The net proceeds from the sale of the bonds replenished corporate
funds used for the February 1997 maturity of $25 million of 5-1/2% First
Mortgage Bonds and general corporate purposes.

CONTINGENCIES

The company is involved in legal or administrative proceedings before
various courts and agencies with respect to rates, taxes and other matters.

Until the early 1950s, certain manufactured gas facilities were operated in
the Nicor Gas service territory.  Manufactured gas is now known to have
created various by-products that may still be present at these sites. 
Current environmental laws may require cleanup of these former manufactured
gas plant sites.  The company has identified up to 40 properties in its
service territory believed to be the location of such sites.  Of these
properties, Nicor Gas currently owns 15 and formerly owned or leased 13. 
The remaining properties were never owned or leased by the company. 
Information regarding preliminary reviews of the company's currently owned
and formerly owned or leased properties has been presented to the Illinois
Environmental Protection Agency.  More detailed investigations are either
currently in progress or planned at many of these sites.  The results of
continued testing and analysis should determine to what extent remediation
is necessary and may provide a basis for estimating any additional future
costs which, based on industry experience, could be significant.  Since
1994, the company has been recovering these costs from its customers in
accordance with Ill.C.C. authorization.




Nicor Gas                                                            Page 6 

Notes to the Consolidated Financial Statements (Unaudited)
(Concluded)

CONTINGENCIES (Concluded)

At certain sites, the current owners are seeking to allocate cleanup costs
to former owners or lessees, including Nicor Gas.

On December 20, 1995, Nicor Gas filed suit in the Circuit Court of Cook
County against insurance carriers seeking recovery of environmental cleanup
costs of certain former manufactured gas plant sites.  Presently, management
cannot predict the outcome of this lawsuit.  Any recoveries from such
litigation or other sources will be flowed back to the company's customers.

Although unable to determine the outcome of these contingencies, management
believes that appropriate accruals have been recorded.  Final disposition of
these matters is not expected to have a material impact on the company's
financial condition or results of operations.

Nicor Gas has entered into agreements to sell, subject to Ill.C.C. approval,
certain nonutility properties with a book value of approximately $6 million
for nearly $17 million.  Sale closings are expected to take place over the
next two quarters.




Nicor Gas                                                            Page 7 

Item 2.  Management's Discussion and Analysis of Financial
         Condition and Results of Operations

The following discussion should be read in conjunction with the Management's
Discussion and Analysis section of the Nicor Gas 1996 Annual Report on Form
10-K.

RESULTS OF OPERATIONS

Net income for the third quarter of 1997 increased to $15.6 million from
$12.8 million in the third quarter of 1996 due primarily to higher
deliveries of natural gas unrelated to weather.  For the nine months ended
September 30, 1997, net income decreased to $74.5 million from $76.4 million
a year ago.  The decrease included the impact of a rate order that was
implemented in April 1996 which included rate design changes and a
depreciation rate increase.  The rate design changes had a positive impact
on 1996 results but a negative impact on first quarter 1997 results when
compared to the prior year.  Net income for the twelve months ended
September 30, 1997, decreased to $105.2 million from $106.1 million a year
ago due to higher depreciation.

Operating revenues decreased $9.9 million for the three-month period and
increased $116.8 million and $211.8 million for the nine- and twelve-month
periods, respectively.  In each period the change was due to variances in
natural gas supply costs, which are recovered from customers.

Margin, defined as operating revenues less cost of gas and revenue taxes,
which are both passed directly through to customers, is shown in the
following table for the periods ended September 30.  For the three-month
period, margin increased due largely to higher deliveries of natural gas. 

                        Three months      Nine months    Twelve months
                        1997     1996    1997    1996    1997    1996 

    Margin (Millions)  $ 88.1   $ 84.1  $356.7  $359.8  $499.5  $495.9

    Margin per Mcf
      delivered          1.35     1.35     .95     .93     .91     .89

Operating and maintenance expenses declined in all periods due, in part, to
ongoing cost control initiatives which more than offset a higher provision
for uncollectible accounts.

Depreciation expense increased in all periods due to the change in the
composite depreciation rate and plant additions.  For further information on
the change in the composite depreciation rate, see Accounting Policies on
page 5.

Interest income increased in each period due to higher investment levels.

Interest on debt increased in the nine- and twelve-month periods due
primarily to higher borrowing levels.  Other interest expense decreased in
the same periods due to a change in interest on income tax adjustments.




Nicor Gas                                                            Page 8 

Item 2.  Management's Discussion and Analysis of Financial
         Condition and Results of Operations (Continued)    

FINANCIAL CONDITION

Net cash flow from operating activities increased $243 million and
$275 million for the nine- and twelve-month periods, respectively, due
primarily to the timing of gas cost recoveries.  Net cash flow from
operations may swing sharply from one interim period to another due to the
seasonal nature of Nicor Gas' business. The company generally relies on
short-term financing to meet temporary increases in working capital needs.  

The company maintains short-term credit agreements with major domestic and
foreign banks.  At September 30, 1997, these agreements, which serve as
backup for the issuance of commercial paper, totaled $250 million, and the
company had $108.1 million of commercial paper outstanding.  At
September 30, 1997, the unused lines of credit under these credit agreements
were $141.9 million.

In October 1997, Nicor Gas issued $50 million of 7-3/8% First Mortgage Bonds
due in 2027.  The net proceeds from the sale of the bonds will be used,
together with other corporate funds, for the November 1997 retirement of $50
million of 9% First Mortgage Bonds due in 2019.
 
In June 1997, Nicor Gas sold $50 million of 6.75% First Mortgage Bonds due
in 2002.  The net proceeds from the sale of the bonds replenished corporate
funds used for the February 1997 maturity of $25 million of 5-1/2% First
Mortgage Bonds and general corporate purposes.

OTHER

Sale of Properties.  Nicor Gas has entered into agreements to sell, subject
to Ill.C.C. approval, certain nonutility properties with a book value of
approximately $6 million for nearly $17 million.  Sale closings are expected
to take place over the next two quarters.

Rate Proceeding.  In June 1997, the Third District Appellate Court of
Illinois upheld the company's general rate increase granted by the Ill.C.C.
on April 3, 1996.  For further information, see Rate Proceeding on page 5.

Customer Select Pilot Program.  On October 8, 1997, the Ill.C.C. approved
Nicor Gas' plans for a three-year pilot program called Customer Select that
will give more customers the opportunity to choose their natural gas
supplier.  Currently over 10 percent of the company's commercial and
industrial customers purchase natural gas from other suppliers, and in the
Customer Select pilot program, the remaining 150,000 commercial and
industrial customers will be eligible to choose their suppliers.  In the
first year, as many as 20,000 of those customers will be able to enroll in
the program.  In the year 2000, up to 10,000 residential customers will be
eligible to sign up.



<TABLE>
Nicor Gas                                                                                           Page 9  

Item 2.  Management's Discussion and Analysis of Financial Condition
         and Results of Operations (Concluded)

OPERATING STATISTICS

Changes in weather can materially affect operating results.  Operating revenues, deliveries, weather
statistics and other data are presented below.
<CAPTION>
                                          Three months ended      Nine months ended      Twelve months ended
                                             September 30            September 30            September 30   
                                           1997       1996         1997       1996         1997       1996  
Operating revenues (Millions):           
 Sales
    <S>                                  <C> <C>    <C>          <C>        <C>          <C>        <C>
    Residential                          $   93.4   $  104.7     $  776.3   $  703.9     $1,112.6   $  982.2
    Commercial                               21.1       23.9        219.8      187.2        314.5      256.9
    Industrial                                5.0        3.4         44.7       33.9         65.2       45.1
                                            119.5      132.0      1,040.8      925.0      1,492.3    1,284.2  
 Transportation
    Commercial                                9.3        7.8         38.6       38.7         55.6       55.0  
    Industrial                               10.8       10.7         34.9       40.4         48.5       57.6
                                             20.1       18.5         73.5       79.1        104.1      112.6

  Revenue taxes and other                    11.5       10.5        100.8       94.2        130.6      118.4

                                         $  151.1   $  161.0     $1,215.1   $1,098.3     $1,727.0   $1,515.2

Deliveries (Bcf):
  Sales                                                                                  
    Residential                              15.7       15.5        157.5      166.3        238.2      249.3
    Commercial                                3.6        3.7         44.8       44.8         67.0       65.2
    Industrial                                1.5         .6         10.6        8.9         16.6       12.4
                                             20.8       19.8        212.9      220.0        321.8      326.9
  Transportation
    Commercial                                6.3        6.3         44.6       51.4         66.7       74.6
    Industrial                               37.9       36.1        119.6      114.9        158.9      158.7
                                             44.2       42.4        164.2      166.3        225.6      233.3 

                                             65.0       62.2        377.1      386.3        547.4      560.2

Average gas cost per Mcf sold            $   2.45   $   3.27     $   3.57   $   2.94     $   3.40   $   2.75

Weather statistics:
  Degree days                                  51         84        4,046      4,088        6,387      6,414
  Percent colder (warmer) than normal       (42.0)      (4.6)         2.8        3.9          4.4        5.1

Customers at end of period (Thousands):
 Sales
    Residential                           1,690.2    1,670.3        
    Commercial                              140.0      139.1
    Industrial                               11.1       11.4
                                          1,841.3    1,820.8
 Transportation                          
    Commercial                               18.7       17.9
    Industrial                                2.9        2.7
                                             21.6       20.6

                                          1,862.9    1,841.4 
</TABLE>



Nicor Gas                                                            Page 10

PART II - Other Information

Item 1.  Legal Proceedings

         For information concerning legal proceedings, see Rate Proceeding
         and Contingencies in Notes to the Consolidated Financial Statements
         beginning on page 5, which are incorporated herein by reference.

Item 6.  Exhibits and Reports on Form 8-K

  (a)    See Exhibit Index on page 12 filed herewith.

  (b)    The company did not file a report on Form 8-K during the third
         quarter of 1997.





Nicor Gas                                                            Page 11

Signature

Pursuant to the requirements of the Securities Exchange Act of 1934, the
registrant has duly caused this report to be signed on its behalf by the
undersigned thereunto duly authorized.



                                   Nicor Gas



Date   November 13, 1997           By        DAVID L. CYRANOSKI        
                                             David L. Cyranoski
                                            Senior Vice President,
                                           Secretary and Controller




Nicor Gas                                                            Page 12

Exhibit Index

 Exhibit
 Number                        Description of Document                      

  1.01    Underwriting agreement, dated October 23, 1997, between Nicor Gas
          and Merrill Lynch & Co.

  4.01    Supplemental Indenture, dated October 15, 1997, of Nicor Gas to
          Harris Trust and Savings Bank, Trustee, under Indenture dated as
          of January 1, 1954.

 12.01    Computation of Consolidated Ratio of Earnings to Fixed Charges.

 27.01    Financial Data Schedule.






<PAGE>
                                                                   
                                                                   Nicor Gas
                                                                   Form 10-Q
                                                                   Exhibit 1.01


                         NORTHERN ILLINOIS GAS COMPANY
 
                                  $50,000,000
 
                             FIRST MORTGAGE BONDS
 
                      7 3/8% SERIES DUE OCTOBER 15, 2027
 
                            UNDERWRITING AGREEMENT
 
Merrill Lynch, Pierce, Fenner & Smith
     Incorporated
World Financial Center
North Tower
New York, NY 10281
As Representative of the several Underwriters
 
                                                               October 23, 1997
 
Dear Sirs:
 
  Northern Illinois Gas Company (the "Company") proposes, subject to the terms
and conditions stated herein and in the General Terms and Conditions of
Underwriting Agreement in the form of Annex A hereto, a copy of which you have
previously received, to issue and sell to the Underwriters named in Schedule I
hereto (the "Underwriters"), $50,000,000 aggregate principal amount of the
Company's First Mortgage Bonds (the "Bonds"). All of the provisions of such
General Terms and Conditions of Underwriting Agreement are incorporated herein
by reference in their entirety, and shall be deemed to be a part of this
Underwriting Agreement to the same extent as if such provisions had been set
forth in full herein. Unless otherwise defined herein, terms defined in the
General Terms and Conditions of Underwriting Agreement are used herein as
therein defined.
 
  An amendment to the Registration Statement, or a supplement to the
Prospectus, as the case may be, relating to the Bonds in the form heretofore
delivered to you is now proposed to be filed or mailed for filing with the
Commission. Such amendment or supplement sets forth the terms of the Bonds.
 
  Subject to the terms and conditions set forth herein, the Company agrees to
issue and sell to the Underwriters and the Underwriters agree to purchase from
the Company, the principal amount of Bonds set forth opposite the name of such
Underwriters in Schedule I hereto on the following terms and conditions:
 
<TABLE>
<S>                                          <C>
  Aggregate principal amount of Bonds to be
   purchased:..............................  $50,000,000
  Rate of interest per annum to be borne by  7 3/8% (such rate to be a multiple of
   the Bonds (payable semiannually):.......  .001%)
  Maturity date of the Bonds:..............  October 15, 2027
  Price to be paid to the Company for the    99.000% of the principal amount of the
   Bonds:                                    Bonds (not less than 99%) plus accrued
                                             interest from date of Supplemental
                                             Indenture to the date of delivery of the
                                             Bonds.
  Initial public offering price of the       99.500% of the principal amount of the
   Bonds:..................................  Bonds plus accrued interest from the date
                                             of Supplemental Indenture to the date of
                                             delivery of the Bonds. (If other, give
                                             details.)
</TABLE>
 
 
                                       1
<PAGE>
 
<TABLE>
<S>                                          <C>
  Place for delivery of Bonds:.............  The Depository Trust Company
                                             55 Water Street
                                             New York, NY 10004
  Date and time of Time of Delivery:.......  October 30, 1997 at 9:00 a.m. Chicago time
  Place for checking Bonds on the business
   day prior to Time of Delivery:..........  The Depository Trust Company, 55 Water
                                             Street, New York, New York 10004
  Redemption and Sinking Fund:.............  Any redemption provisions will be as set
                                             forth on Schedule II hereto. No sinking
                                             fund will be provided.
  Address for notices per Section 12 of the
   General Terms and Conditions of           Merrill Lynch, Pierce, Fenner & Smith
   Underwriting Agreement:.................           Incorporated
                                             World Financial Center
                                             North Tower
                                             New York, NY 10281
</TABLE>
 
 
  If the foregoing is in accordance with your understanding, please sign and
return to us the enclosed counterparts hereof, whereupon it will become a
binding agreement between the Underwriters and the Company in accordance with
its terms. It is understood that your acceptance of this letter on behalf of
each of the Underwriters constitutes your representation that you are
authorized to execute this Underwriting Agreement on behalf of the
Underwriters.
 
                                          Very truly yours,
 
                                          Northern Illinois Gas Company
 
 
                                          By __________________________________
                                          Title: ______________________________
The foregoing Underwriting Agreement
 is hereby confirmed and accepted as
 of the date first above written.
 
Merrill Lynch, Pierce, Fenner & Smith
           Incorporated
 
 
By __________________________________
Title: ______________________________
 
On behalf of itself and as
 Representative of each of the
 Underwriters named in Schedule I
 hereto.
 
                                       2
<PAGE>
 
                                                                    SCHEDULE I
 
<TABLE>
<CAPTION>
                                                                     PRINCIPAL
                                                                     AMOUNT OF
      NAME OF UNDERWRITER                                              BONDS
      -------------------                                           -----------
      <S>                                                           <C>
      Merrill Lynch, Pierce, Fenner & Smith Incorporated........... $17,500,000
      Salomon Brothers Inc.........................................  17,500,000
      ABN AMRO Chicago Corporation ................................  15,000,000
                                                                    -----------
        Total...................................................... $50,000,000
                                                                    ===========
</TABLE>
<PAGE>
 
                                                                    SCHEDULE II
 
  Redemption. The Bonds may not be called for redemption by the Company prior
to October 15, 2002. On October 15, 2002 and thereafter until maturity on
October 15, 2027, the Bonds may be redeemed at the Company's option, on not
less than 30 nor more than 45 days notice, as a whole at any time, or in part
from time to time, at the following redemption prices (expressed as
percentages of principal amount) plus accrued and unpaid interest to the date
fixed for redemption.
 
  If redeemed during the twelve month period beginning October 15:
 
<TABLE>
<CAPTION>
                        REDEMPTION
YEAR                      PRICE
- ----                    ----------
<S>                     <C>
2002...................   105.16%
2003...................   104.82
2004...................   104.47
2005...................   104.13
2006...................   103.79
2007...................   103.44
2008...................   103.10
</TABLE>
<TABLE>
<CAPTION>
                        REDEMPTION
YEAR                      PRICE
- ----                    ----------
<S>                     <C>
2009...................   102.75%
2010...................   102.41
2011...................   102.07
2012...................   101.72
2013...................   101.38
2014...................   101.04
2015...................   100.69
2016...................   100.35
</TABLE>
 
and thereafter at 100% of the principal amount thereof.
<PAGE>
 
                                                                        ANNEX A
 
                         NORTHERN ILLINOIS GAS COMPANY
 
                                  $50,000,000
 
                             FIRST MORTGAGE BONDS
 
            GENERAL TERMS AND CONDITIONS OF UNDERWRITING AGREEMENT
 
  Northern Illinois Gas Company, an Illinois corporation (the "Company"),
proposes to enter into an Underwriting Agreement into which these General
Terms and Conditions are incorporated by reference (the "Underwriting
Agreement") and, subject to the terms and conditions stated therein, to issue
and sell to the underwriter or underwriters named in Schedule I to the
Underwriting Agreement $50,000,000 aggregate principal amount of its First
Mortgage Bonds (hereinafter called the "Bonds") under the registration
statement referred to in Section 2(a) hereof. Such Bonds will be issued under
the Company's Indenture dated as of January 1, 1954, to Harris Trust and
Savings Bank, Trustee (the "Trustee"), as supplemented by supplemental
indentures dated February 9, 1954, April 1, 1956, June 1, 1959, July 1, 1960,
June 1, 1963, July 1, 1963, August 1, 1964, August 1, 1965, May 1, 1966,
August 1, 1966, July 1, 1967, June 1, 1968, December 1, 1969, August 1, 1970,
June 1, 1971, July 1, 1972, July 1, 1973, April 1, 1975, April 30, 1976, April
30, 1976, July 1, 1976, August 1, 1976, December 1, 1977, January 15, 1979,
December 1, 1981, March 1, 1983, October 1, 1984, December 1, 1986, March 15,
1988, July 1, 1988, July 1, 1989, July 15, 1990, August 15, 1991, July 15,
1992, February 1, 1993, March 15, 1993, May 1, 1993, July 1, 1993, August 15,
1994, October 15, 1995, May 10, 1996, August 1, 1996 and June 1, 1997
respectively, and as to be further supplemented by a Supplemental Indenture
(the "Supplemental Indenture") which will be dated the first or fifteenth day
of the calendar month in which the "Time of Delivery" (as hereinafter defined)
falls, creating the series in which the Bonds are to be issued. Said Indenture
as so supplemented is hereinafter called the "Indenture." The term
"Underwriters" herein shall refer to the several persons, firms and
corporations named in Schedule I to the Underwriting Agreement and the term
"Representatives" herein shall refer to the Underwriters identified as the
Representatives who are acting on behalf of the Underwriters (including
themselves) in the Underwriting Agreement. All obligations of the Underwriters
under the Underwriting Agreement are several and not joint. The terms
"Underwriters", "Representatives", "persons", "firms" and "corporations" shall
include the singular as well as the plural.
 
  The terms of the issuance of the Bonds shall be as specified in the
Underwriting Agreement. The Underwriting Agreement shall constitute an
agreement by the Company and the Underwriters to be bound by all of the
provisions of these General Terms and Conditions of Underwriting Agreement, as
follows:
 
  Section 1. Sale of Bonds. Sales of the Bonds will be made to the
Underwriters, for whom the Representatives will act as such. The obligation of
the Company to issue and sell any of the Bonds and the obligation of any of
the Underwriters to purchase any of the Bonds shall be evidenced by the
Underwriting Agreement. The Underwriting Agreement shall specify the aggregate
principal amount of Bonds to be purchased, the rate and time of payment of
interest to be borne by the Bonds, the maturity date of the Bonds, the price
to be paid to the Company for the Bonds, the initial public offering price or
other offering terms of such Bonds and the redemption prices and other special
terms, if any, relating to the Bonds, the names of the Underwriters of such
Bonds, the names of the Representatives of such Underwriters and the amount of
Bonds to be purchased by each Underwriter, and, subject to the provisions of
Section 3 hereof, shall set forth the date, time and manner of the delivery of
such Bonds. The terms of the Bonds will be set forth in the Prospectus
Supplement (as hereinafter defined). The Underwriting Agreement shall be in
the form of an executed writing (which may be in counterparts) and may be
evidenced by an exchange of telecopied communications or any other rapid
transmission device to produce a written record of communications transmitted.
<PAGE>
 
  Section 2. Representations and Warranties of the Company. The Company
represents and warrants to, and agrees with, the several Underwriters that:
 
    (a) A registration statement on Form S-3 with respect to the Bonds,
  including a related preliminary prospectus, has been prepared by the
  Company in conformity with the requirements of the Securities Act of 1933,
  as amended (the "Act"), and the rules and regulations of the Securities and
  Exchange Commission (the "Commission") under the Act (the "Regulations"),
  and has been filed with the Commission on April 18, 1994 and, if one or
  more amendments to such registration statement, which may include an
  amended preliminary prospectus, have been filed with the Commission, such
  amendments have been similarly prepared; and such registration statement
  has become effective. Such registration statement, as amended to the date
  of the Underwriting Agreement, together with the prospectus supplement
  referred to below is hereinafter referred to as the "Registration
  Statement". Such prospectus as supplemented specifically relating to the
  Bonds and filed with the Commission under Rule 424(b) of the Act is
  hereinafter referred to as the "Prospectus". The Prospectus has been
  prepared by the Company in conformity with the requirements of the Act and
  the Regulations. Copies of the Registration Statement and any related
  prospectus have been delivered to the Representatives. As used herein,
  Registration Statement, Prospectus and preliminary prospectus shall
  include, in each case, the material incorporated therein pursuant to Item
  12 of Form S-3 filed under the Securities Exchange Act of 1934 (the "1934
  Act") on or prior to the date of the Underwriting Agreement, and "amended",
  "amendment" or "supplement" with respect to the Registration Statement or
  the Prospectus shall be deemed to include the filing by the Company of any
  document pursuant to Sections 13(a), 13(c), 14 or 15(d) of the 1934 Act
  after the date of the Underwriting Agreement.
 
    (b) The registration statement at the time it became effective, and the
  related prospectus and any amendments and supplements thereto filed prior
  to the date of the Underwriting Agreement, conformed in all material
  respects to the provisions of the Act and the Trust Indenture Act of 1939,
  as amended (the "Trust Indenture Act") and the rules and regulations of the
  Commission thereunder, on the date of the Underwriting Agreement and at the
  Time of Delivery (referred to in Section 3) the Registration Statement, the
  Prospectus, and any amendments and supplements thereto, and the Indenture,
  will conform in all material respects to the Act, the Trust Indenture Act
  and the respective rules and regulations of the Commission thereunder, and
  at the time the registration statement became effective, the registration
  statement and related prospectus did not contain any untrue statement of a
  material fact or omit to state a material fact required to be stated
  therein or necessary to make the statements therein not misleading; and at
  the date of this Underwriting Agreement and at the Time of Delivery, the
  Registration Statement and the Prospectus and any amendments and
  supplements thereto do not and will not contain any untrue statement of a
  material fact or omit to state a material fact necessary in order to make
  the statements therein not misleading; provided, however, that none of the
  representations and warranties in this subsection shall apply to statements
  in or omissions from the Registration Statement or Prospectus or any
  amendment or supplement thereto made in reliance upon and in conformity
  with information respecting the Underwriters furnished to the Company in
  writing by or on behalf of any Underwriter through the Representatives
  expressly for use in the Registration Statement or Prospectus.
 
    (c) The documents incorporated by reference into the Prospectus, at the
  time they were filed with the Commission, complied in all material respects
  with the requirements of the 1934 Act and the rules and regulations of the
  Commission thereunder (the "1934 Regulations"), and, at the date of this
  Underwriting Agreement and at the Time of Delivery, when read together with
  the Prospectus and any supplement thereto will not contain an untrue
  statement of a material fact or omit to state a material fact required to
  be stated therein or necessary to make the statements therein not
  misleading, and any documents filed after the date of the Underwriting
  Agreement and so incorporated by reference in the Prospectus will, when
  they are filed with the Commission, comply in all material respects with
  the requirements of the 1934 Act and the 1934 Regulations, and when read
  together with the Prospectus and any supplement thereto will not contain an
  untrue statement of material fact or omit to state a material fact required
  to be stated therein or necessary to make the statements therein not
  misleading.
 
                                       2
<PAGE>
 
    (d) Arthur Andersen LLP are independent public accountants with respect
  to the Company and its subsidiaries as required by the Act and the
  Regulations.
 
    (e) The financial statements included in the Registration Statement
  present fairly the financial position of the Company and its consolidated
  subsidiaries as of the dates indicated and the results of their operations
  for the periods specified, and said financial statements have been prepared
  in conformity with generally accepted accounting principles applied on a
  consistent basis during the periods involved.
 
    (f) The Company is a corporation in good standing, duly organized and
  validly existing under the laws of Illinois, and has due corporate
  authority to carry on the business in which it is engaged and to own and
  operate the properties used by it in such business as described in the
  Prospectus. The Company's subsidiary constitutes less than 5% of its
  consolidated assets and during the year ended December 31, 1996 contributed
  less than 5% of its consolidated annual operating revenues and net income,
  and the Company does not consider its subsidiary to be material.
 
    (g) The execution and delivery of the Underwriting Agreement have been
  duly authorized by the Company and the Underwriting Agreement constitutes a
  valid and legally binding obligation of the Company; the Bonds have been
  duly authorized, and when issued and delivered pursuant to the Underwriting
  Agreement and the Indenture, will have been duly executed, authenticated,
  issued and delivered and will constitute valid and legally binding
  obligations of the Company in accordance with their respective terms,
  entitled to the benefits provided by the Indenture; the Supplemental
  Indenture has been duly authorized in substantially the form filed as an
  exhibit to the Registration Statement and, when executed and delivered by
  the Company and the Trustee, will constitute a valid and legally binding
  instrument enforceable in accordance with its terms, except to the extent
  the enforceability of the Bonds and the Indenture may be limited by
  bankruptcy, insolvency, reorganization or other laws of general application
  relating to or affecting the enforcement of creditors' rights or general
  equity principles; and the Indenture and the Bonds as executed and
  delivered will conform in all material respects to the descriptions thereof
  in the Prospectus.
 
    (h) The issue and sale of the Bonds and the compliance by the Company
  with all of the provisions of the Bonds, the Indenture, and the
  Underwriting Agreement and the transactions contemplated thereby will not
  conflict with or result in any breach or violation of any of the provisions
  of, or constitute (disregarding any grace or notice period) a default
  under, or result in the imposition of any lien, charge or encumbrance upon
  any property or assets of the Company pursuant to the terms of, any other
  indenture, or any mortgage, loan agreement, contract, note, lease or other
  agreement or instrument to which the Company is a party or by which the
  Company may be bound or to which any of the property or assets of the
  Company is subject, nor will such action result in any violation of the
  provisions of the charter or by-laws of the Company or any statute or any
  order, rule or regulation applicable to the Company of any court or any
  federal, state or other regulatory authority or other governmental body
  having jurisdiction over the Company or any of its properties.
 
    (i) Since the respective dates as of which information is given in the
  Registration Statement and Prospectus and except as may otherwise be stated
  or contemplated therein; (i) there has not been any material adverse change
  in the condition, financial or otherwise, of the Company and its
  subsidiaries considered as one enterprise, or in the earnings, affairs,
  business prospects or properties of the Company and its subsidiaries
  considered as one enterprise, whether or not arising in the ordinary course
  of business or arising from any court or governmental action, order or
  decree, and (ii) there has been no transaction entered into by the Company
  or any subsidiary which is material to the Company and its subsidiaries
  considered as one enterprise, other than transactions in the ordinary
  course of business.
 
    (j) Except as set forth in the Prospectus, the Company, with minor
  exceptions, and subject to noncompliance with certain procedural and other
  requirements in the procurement and granting of gas franchises in a number
  of smaller municipalities formerly served by Mid-Illinois Gas Company, has
  statutory authority, franchises, licenses, rights-of-way, easements and
  consents, free from unduly burdensome restrictions and adequate for the
  conduct of the business in which it is engaged.
 
 
                                       3
<PAGE>
 
    (k) The Illinois Commerce Commission has entered an order authorizing the
  issue and sale of the Bonds by the Company upon terms consistent with the
  Underwriting Agreement, and no other consent, approval, authorization or
  other order or filing with any regulatory or governmental body is required
  for the issuance and sale of the Bonds and consummation of the transactions
  contemplated hereby, except such consents, approvals, authorizations,
  registrations or qualifications as may be required under state securities
  or Blue Sky laws in connection with the purchase and distribution of the
  Bonds by the Underwriters.
 
    (l) The Company is not in violation of its charter or, except as
  disclosed in the Prospectus, in default in the performance or observance of
  any obligation, agreement, covenant or condition contained in any contract,
  indenture, mortgage, loan agreement, note, lease or other instrument to
  which it is a party or by which it or its property is bound or affected
  which is material to the Company and its subsidiary considered as one
  enterprise.
 
    (m) Except as set forth in the Registration Statement and Prospectus,
  there are no legal or governmental proceedings pending to which the Company
  or its subsidiary is a party or of which any property of the Company or its
  subsidiary is the subject, and, to the best of the Company's knowledge, no
  such proceedings are threatened or contemplated by governmental authorities
  or threatened by others, other than proceedings which, if determined
  adversely to the Company and its subsidiary, would not individually or in
  the aggregate have a material adverse effect on the business, properties,
  financial position, net worth or results of operations of the Company and
  its subsidiary considered as a whole.
 
  Any certificate signed by any officer of the Company and delivered to you or
to Underwriters' counsel shall be deemed a representation and warranty by the
Company to each Underwriter as to the statements made therein.
 
  Section 3. Purchase, Sale and Delivery of Bonds. Following the execution of
the Underwriting Agreement, the several Underwriters propose to make a public
offering of their respective portions of the Bonds as soon as in the
Representatives' judgment it is advisable upon the terms and conditions set
forth in the Prospectus Supplement.
 
  The Bonds to be purchased by each Underwriter pursuant to the Underwriting
Agreement, in definitive form and registered in such names as the
Representatives may request upon at least forty-eight hours' prior notice to
the Company, shall be delivered by or on behalf of the Company to the
Representatives for the respective accounts of the several Underwriters,
against payment therefor as specified in the Underwriting Agreement in
immediately available funds, at the office of Mayer, Brown & Platt, 190 South
LaSalle Street, Chicago, Illinois 60603 (except as hereinafter provided with
respect to delivery of such Bonds), at the time and date specified in the
Underwriting Agreement or at such other place and time and date as the
Representatives and the Company may agree upon in writing, such time and date
being herein called the "Time of Delivery". If specified by the
Representatives in the Underwriting Agreement, delivery of the Bonds will be
made at the Time of Delivery at such place in New York, New York as shall have
been so specified against payment therefor in Chicago as aforesaid.
 
  Section 4. Covenants of the Company. The Company covenants with each
Underwriter that:
 
    (a) The Company will notify the Representatives immediately and confirm
  the notice in writing (i) of the receipt of any request by the Commission
  for any amendment or supplement to the Registration Statement or the
  Prospectus or any amendment or supplement thereto or for additional
  information, and (ii) of the issuance by the Commission of any stop order
  suspending the effectiveness of the Registration Statement or of the
  initiation or threatened initiation of any proceedings for that purpose or
  of the suspension or threatened suspension of the qualification of the
  Bonds for offering or sale in any jurisdiction. The Company will make every
  reasonable effort to prevent the issuance by the Commission of any stop
  order and, if any such stop order shall at any time be issued, to obtain
  the lifting thereof at the earliest moment.
 
 
                                       4
<PAGE>
 
    (b) The Company will not file any amendment to the Registration Statement
  or any amendment or supplement to the Prospectus (including a prospectus
  filed pursuant to Rule 424 and including documents deemed to be
  incorporated by reference into the Prospectus) without first having
  furnished the Representatives with a copy of the proposed form thereof and
  given the Representatives a reasonable opportunity to review and comment
  respecting the same and having given reasonable consideration to any
  comments or objections made by the Representatives.
 
    (c) The Company will deliver to each of the Representatives, as soon as
  available, one signed copy of the Registration Statement as originally
  filed and of each amendment thereto, including, in each case, documents
  incorporated by reference into the Registration Statement and one set of
  exhibits thereto (other than exhibits incorporated by reference which will
  be furnished upon specific request), and will also deliver to the
  Representatives a reasonable number of conformed copies of the Registration
  Statement as originally filed and of each amendment and post-effective
  amendment thereto including such incorporated documents (without exhibits)
  for each of the Underwriters.
 
    (d) The Company will deliver to each Underwriter from time to time during
  the period when a prospectus is required to be delivered under the Act such
  number of copies of the Prospectus (as amended or supplemented and
  including incorporated documents) as the Representatives may reasonably
  request for the purposes contemplated by the Act or the Regulations;
  provided, however, that the delivery of copies of the Prospectus (as
  amended or supplemented and including incorporated documents) more than
  nine months after the date of the Underwriting Agreement shall be at the
  expense of the Underwriter requesting such delivery.
 
    (e) During the period when a prospectus is required to be delivered under
  the Act, the Company will comply so far as it is able, and at its own
  expense (for a period not to exceed nine months), with all requirements
  imposed upon it by the Act, and by Sections 13 and 14 of the 1934 Act, as
  now or hereafter amended, and by the Regulations, as from time to time in
  force, so far as necessary to permit the continuance of sales of or dealing
  in the Bonds during such period in accordance with the provisions hereof
  and of the Prospectus.
 
    (f) If any event shall occur as a result of which it is necessary, in the
  opinion of counsel for the Company and of Underwriters' counsel, to amend
  or supplement the Prospectus in order to make the Prospectus not misleading
  in the light of the circumstances existing at the time it is delivered to a
  purchaser, or if it is necessary to amend or supplement the Prospectus to
  comply with law, the Company will forthwith prepare and furnish to the
  Underwriters, without expense to them except as otherwise provided in
  subsection (d) of this Section 4, a reasonable number of copies of an
  amendment or amendments or a supplement or supplements to the Prospectus
  (in the form referred to in subsection (b) of this Section 4) which will
  amend or supplement the Prospectus so that as amended or supplemented it
  will not contain any untrue statement of a material fact or omit to state
  any material fact necessary in order to make the statements therein not
  misleading, or so that the Prospectus will comply with law. For the
  purposes of this subsection, the Company will furnish such information as
  the Representatives may from time to time reasonably request.
 
    (g) The Company will endeavor in good faith, in cooperation with the
  Underwriters, to qualify the Bonds for offering and sale under the
  applicable securities laws of such jurisdictions as the Representatives may
  designate and to arrange for the determination of the legality of the Bonds
  for purchase by institutional investors; provided, however, that the
  Company shall not be obligated to file any general consent to service or to
  qualify as a foreign corporation or as a dealer in securities in any
  jurisdiction in which it is not so qualified. In each jurisdiction where
  any of the Bonds shall be qualified as above provided, the Company will
  make and file such statements and reports in each year as are or may be
  reasonably required by the laws thereof.
 
    (h) The Company will make generally available to its security holders as
  soon as practicable, but not later than 75 days after the close of the
  period covered thereby, an earnings statement (in form complying with the
  provisions of Section 11(a) of the Act and the Regulations thereunder
  (including, at the option of
 
                                       5
<PAGE>
 
  the Company, Rule 158), which need not be certified by independent public
  accountants unless required by the Act or the Regulations), covering a
  twelve-month period beginning on the first day of the calendar quarter
  following the Time of Delivery.
 
    (i) The Company agrees that it will not publicly offer or sell any
  intermediate or long-term debt between the date of the Underwriting
  Agreement and Time of Delivery without the prior written consent of the
  Representatives.
 
  Section 5. Payment of Expenses. The Company will pay all expenses incident
to the performance of its obligations under the Underwriting Agreement,
including (i) the printing and filing by the Company of the registration
statement and the printing of the Underwriting Agreement, any Agreement Among
Underwriters, any Selling Agreement, the Supplemental Indenture and the
Underwriters' Questionnaire, (ii) the authorization, issuance and delivery of
the Bonds to the Underwriters, including the printing and engraving of the
Bonds, and all taxes, if any, upon the issuance and sale of the Bonds to the
Underwriters, (iii) the qualification of the Bonds under the securities laws
of the various jurisdictions in accordance with the provisions of subsection
(g) of Section 4, including filing fees and fees and disbursements of
Underwriters' counsel in connection with such qualification and in connection
with the preparation of the Blue Sky Survey (such fees of Underwriters'
counsel not to exceed $6,500 in the aggregate), (iv) any fees charges by
securities rating services for rating the Bonds, (v) the fees and expenses of
the Trustee and its counsel in connection with the Bonds and the Supplemental
Indenture, (vi) the printing and delivery to the Underwriters and dealers in
quantities as hereinbefore stated of copies of the registration statement and
all amendments thereto, of any preliminary prospectuses and amended
preliminary prospectuses, of the Registration Statement and any amendments
thereto, and of the Prospectus and any amendments or supplements thereto, and
(vii) the cost of printing and delivery to the Underwriters of copies of the
Blue Sky Survey.
 
  If this Agreement is terminated by the Representatives in accordance with
the provisions of Section 6 or Section 10(b), or is prevented by the Company
from becoming effective in accordance with the provisions of Section 10(a),
the Company shall reimburse the Underwriters severally for their out-of-pocket
expenses, including the reasonable fees and disbursements of counsel for the
Underwriters incurred in connection with the offering.
 
  Section 6. Conditions of Underwriters' Obligations. The several obligations
of the Underwriters hereunder are subject to the accuracy of and compliance
with the representations and warranties of the Company herein contained, to
the performance by the Company of its obligations hereunder and to the
following further conditions:
 
    (a) At the Time of Delivery no stop order suspending the effectiveness of
  the Registration Statement shall have been issued under the Act or
  proceedings therefor initiated or threatened by the Commission.
 
    (b) At the Time of Delivery the Representatives shall have received:
 
      (1) The favorable opinion, dated as of the Time of Delivery, of
    Mayer, Brown & Platt, counsel for the Company, in form and substance
    satisfactory to counsel for the Underwriters, to the effect that:
 
        (i) the Company is a corporation in good standing, duly organized
      and validly existing under the laws of the State of Illinois and has
      due corporate authority to carry on the business in which it is
      engaged and to own and operate the properties used by it in such
      business;
 
        (ii) the Indenture is in due and proper form, has been duly and
      validly authorized by the necessary corporate action and by orders
      duly entered by the Illinois Commerce Commission; no authorization,
      approval, consent, certificate or order of any other state
      commission or regulatory authority or of any federal commission or
      regulatory authority not already obtained is required in respect of
      the execution and delivery of the Indenture; and the Indenture has
      been duly and validly executed and delivered and is a valid and
      enforceable instrument in accordance with its terms,
 
                                       6
<PAGE>
 
      except as enforcement of provisions of the Indenture may be limited
      by bankruptcy or other laws of general application affecting the
      enforcement of creditors' rights and by general equity principles;
 
        (iii) the Bonds are in due and proper form; the issue and sale of
      the Bonds by the Company in accordance with the terms of the
      Underwriting Agreement have been duly and validly authorized by the
      necessary corporate action and by order duly entered by the Illinois
      Commerce Commission; no authorization, approval, consent,
      certificate or order of any other state commission or regulatory
      authority or of any federal commission or regulatory authority not
      already obtained is required in respect of such issue and sale
      (except such consents, approvals, authorizations, registrations or
      qualifications as may be required under state securities or Blue Sky
      laws in connection with the purchase and distribution of the Bonds
      by the Underwriters); the Bonds have been duly executed and
      delivered to the Underwriters against payment of the agreed
      consideration therefor and, assuming due authentication thereof by
      the Trustee, constitute valid and enforceable obligations of the
      Company in accordance with their terms, secured by the lien of and,
      with like exception as noted in the foregoing subdivision (ii),
      entitled to the benefits provided by the Indenture, and the
      registered owners of the Bonds will be entitled to the payment of
      principal and interest, and premium in case of redemption, as
      therein provided; the Bonds and the Indenture conform as to legal
      matters in all material respects with the statements concerning them
      made in the Prospectus, and such statements accurately set forth the
      matters respecting the Bonds and the Indenture required to be set
      forth in the Prospectus;
 
        (iv) The Registration Statement is effective under the Act and the
      Indenture has been duly qualified under the Trust Indenture Act, and
      to the best of the knowledge of said counsel no proceedings for a
      stop order are pending or threatened under Section 8(d) of the Act;
 
        (v) the execution and delivery of the Underwriting Agreement by
      the Company has been duly authorized by the necessary corporate
      action, and the Underwriting Agreement has been duly executed and
      delivered by the Company;
 
        (vi) the Company has good and sufficient title to all property
      described or referred to in the Indenture and purported to be
      conveyed thereby (except property released from the lien of the
      Indenture in connection with the sale or other disposition thereof),
      subject only to the lien of the Indenture and to permitted liens as
      defined therein; the Indenture has been duly filed for recordation
      in such manner and in such places as is required by law in order to
      give constructive notice of, establish, preserve and protect the
      lien of the Indenture; the Indenture constitutes a valid, direct
      first mortgage lien, subject only to permitted liens, on
      substantially all property of the Company, except property expressly
      excepted by the terms of the Indenture; the Indenture will, when
      recorded or registered by the Company in accordance with its
      covenants under the Indenture, constitute a valid, direct first
      mortgage lien on all property of the character of that now subject
      to the lien of the Indenture hereafter acquired by the Company,
      subject only to permitted liens and to liens, if any, existing or
      placed on such after-acquired property at the time of the
      acquisition thereof;
 
        (vii) the issue and sale of the Bonds and the compliance by the
      Company with all of the provisions of the Bonds, the Indenture and
      the Underwriting Agreement will not conflict with or result in a
      breach or violation of any of the provisions of, or constitute
      (disregarding any grace or notice period) a default under, any
      indenture, mortgage, loan agreement, contract, note, lease or other
      agreement or instrument, known to such counsel, to which the Company
      is a party or by which the Company is bound or to which any of the
      property or assets of the Company is subject (with such exceptions
      as are in the aggregate not material to the business or financial
      condition of the Company or the validity of the Bonds), nor will
      such action result in any violation of the provisions of the Charter
      or By-Laws of the Company, or, to the best of their knowledge, any
      statute or any order, rule or regulation applicable to the Company
      of any court or governmental agency or body having jurisdiction over
      the Company or any of its properties (except such
 
                                       7
<PAGE>
 
      consents, approvals, authorizations, registrations or qualifications
      as may be required under state securities or Blue Sky laws in
      connection with the purchase and distribution of the Bonds by the
      Underwriters);
 
        (viii) at the time the registration statement became effective,
      the registration statement and the related prospectus (other than
      the financial statements and notes thereto and supporting schedules
      and other financial information included therein, as to which no
      opinion need be rendered) complied as to form in all material
      respects with the requirements of the Act and the Trust Indenture
      Act and the Regulations;
 
        (ix) with minor exceptions, and subject to noncompliance with
      certain procedural and other requirements in the procurement and
      granting of gas franchises in a number of smaller municipalities
      formerly served by Mid-Illinois Gas Company, the Company holds
      franchises from all of the incorporated cities and villages included
      in the communities in which the Company renders gas service; all of
      the franchises so held by the Company are valid and subsisting and
      authorize it to engage in the business conducted by it in the
      respective municipalities granting such franchises; the Company also
      holds certificates of public convenience and necessity issued by the
      Illinois Commerce Commission, which are valid and subsisting and
      constitute due authorization by such commission for the conduct by
      the Company of its operations in all areas served;
 
        (x) to the best of their knowledge and information, there are no
      contracts, indentures, mortgages, loan agreements, notes, leases or
      other instruments of a character required to be described in the
      Registration Statement or Prospectus or to be filed as exhibits to
      the Registration Statement other than those described therein or
      filed or incorporated by reference as exhibits thereto and the
      descriptions thereof or reference thereto are correct; and
 
        (xi) except as disclosed in the Prospectus, there are no material
      pending or threatened legal proceedings, considering the Company and
      the subsidiaries as a single enterprise, known to said counsel, to
      which the Company or any subsidiary is a party or of which property
      of the Company or any subsidiary is the subject, and to the best of
      the knowledge of said counsel there are no such proceedings
      contemplated by governmental authorities.
 
    Such counsel shall further state that, based upon their participation
    in the preparation of the Registration Statement and the Prospectus,
    and any amendment or supplement thereto, and upon their review and
    discussions of the contents thereof, but without independent check or
    verification except as specified, nothing has come to their attention
    that has caused them to believe that the Registration Statement, at the
    time it became effective, contained an untrue statement of a material
    fact or omitted to state a material fact required to be stated therein
    or necessary to make the statements therein not misleading or that the
    Prospectus, and any amendment or supplement thereto, at the date the
    Registration Statement became effective, the date of this Agreement or
    at the Time of Delivery, contained an untrue statement of a material
    fact or omitted to state a material fact necessary in order to make the
    statements therein, in light of the circumstances under which they were
    made, not misleading.
 
      (2) The favorable opinion of Wildman, Harrold, Allen & Dixon, counsel
    for the Underwriters, with respect to the incorporation of the Company,
    the validity of the Bonds and the Indenture, the Registration
    Statement, the Prospectus and other related matters as the
    Representatives may reasonably request; provided that any opinion
    requested with respect to the jurisdiction of regulatory authorities
    (other than the Illinois Commerce Commission, the Securities and
    Exchange Commission and state securities or Blue Sky authorities) and
    the matters in subdivisions (vi) and (ix) above will rely upon the
    opinion of Mayer, Brown & Platt.
 
    (c) At the effective date of the Registration Statement and at the Time
  of Delivery the Representatives shall have received a letter from Arthur
  Andersen LLP, dated the effective date or Time of Delivery, respectively,
  in form and substance satisfactory to the Representatives, advising that
  (i) they are independent public accountants with respect to the Company and
  its subsidiaries as required by the Act and the 1934
 
                                       8
<PAGE>
 
  Act and the applicable Regulations, (ii) in their opinion, the audited
  consolidated financial statements and any supplemental financial
  information and schedules of the Company examined by them and incorporated
  by reference in the Registration Statement and Prospectus comply as to form
  in all material respects with the applicable accounting requirements of the
  Act, the 1934 Act and the applicable Regulations, (iii) on the basis of a
  reading of the latest available unaudited interim consolidated financial
  statements prepared by the Company, a reading of the minutes of meetings of
  the shareholder and the board of directors and executive committee of the
  Company and its subsidiaries, consultation with officers of the Company
  responsible for financial and accounting matters and other specified
  procedures, nothing has come to their attention which caused them to
  believe that (A) the unaudited interim condensed consolidated financial
  statements included or incorporated by reference in the Prospectus do not
  comply as to form in all material respects with the applicable accounting
  requirements of the Act, the 1934 Act and the applicable Regulations or are
  not in conformity with generally accepted accounting principles applied on
  a basis substantially consistent with that of the audited financial
  statements incorporated as aforesaid, (B) the unaudited amounts set forth
  in "Summary Information--Consolidated Financial Information" and any other
  unaudited income statement data and balance sheet data (other than such
  data for the periods referred to in (A) above) included or incorporated by
  reference in the Prospectus do not agree with the corresponding items in
  the audited or unaudited, as the case may be, financial statements from
  which such data were derived or were not determined on a basis
  substantially consistent with that of the corresponding amounts included in
  the audited consolidated financial statements of the Company incorporated
  in the Registration Statement and Prospectus, or (C) at a specified date
  within five business days of the date of such letter with respect to (1)
  below, and during the period from the date of the latest audited
  consolidated financial statements or unaudited interim condensed
  consolidated financial statements, as the case may be, incorporated in the
  Prospectus to the date of the latest available unaudited interim
  consolidated financial statements (if any) prepared by the Company with
  respect to (2) below, except in all instances as set forth in or
  contemplated by the Prospectus or as set forth in such letter: (1) there
  was any increase in the consolidated long-term debt of the Company and its
  subsidiaries, as compared with the amounts set forth in the latest balance
  sheet included or incorporated by reference in the Prospectus, or (2) there
  were any decreases in consolidated operating income or net income as
  compared with the corresponding period in the preceding year; and (iv) they
  have carried out specified procedures performed for the purpose of
  comparing certain financial information and percentages (which is limited
  to financial information derived from general accounting records of the
  Company) specified by the Representatives and appearing in the Registration
  Statement or in schedules or exhibits to the Registration Statement or in
  the Prospectus or in documents incorporated by reference in the Prospectus
  with indicated amounts in the financial statements or accounting records of
  the Company and (excluding any questions of legal interpretation and, in
  the case of the letter delivered at the Time of Delivery, any exceptions
  disclosed in the letter delivered at the Effective Date) have found such
  information and percentages to be in agreement with the relevant accounting
  and financial information of the Company referred to in such letter in the
  description of the procedures performed by them. If such letter discloses
  any material adverse decreases or increases, as the case may be, in the
  items specified in item (iii) (C) above which are not set forth in or
  contemplated by the Prospectus which, in the judgment of the
  Representatives, makes it impracticable or inadvisable to proceed with the
  public offering or the delivery of the Bonds on the terms and in the manner
  contemplated by the Prospectus, this Agreement and all obligations of the
  Underwriters hereunder may be cancelled by the Representatives by notifying
  the Company in the manner and with the effect provided below in the last
  sentence of this Section 6.
 
    (d) At the Time of Delivery the Representatives shall have received a
  certificate of the Chairman and President, Vice President and principal
  financial officer, Vice President and principal accounting officer or
  Treasurer of the Company, dated as of the Time of Delivery, to the effect
  that the signer of such certificate has carefully examined the Registration
  Statement, the Prospectus and any amendment or supplement thereto and the
  Underwriting Agreement and that, in his opinion, at the time the
  Registration Statement became effective, the Registration Statement did not
  contain an untrue statement of a material fact or omit to state a material
  fact required to be stated therein or necessary in order to make the
  statements therein not misleading, and at the date of the Underwriting
  Agreement the Prospectus did not contain an untrue
 
                                       9
<PAGE>
 
  statement of a material fact or omit to state a material fact required to
  be stated therein or necessary in order to make the statements therein not
  misleading, and since the date of the Underwriting Agreement, no event has
  occurred which should have been set forth in an amendment of or supplement
  to the Prospectus which has not been so set forth; and no stop order
  suspending the effectiveness of the Registration Statement has been issued
  and no proceedings therefor have been instituted or threatened by the
  Commission; and to the further effect that all the representations and
  warranties contained in Section 2 hereof are true and correct, with the
  same force and effect as though expressly made at the Time of Delivery.
 
    (e) At the Time of Delivery counsel for the Underwriters shall have been
  furnished with such documents and opinions as they may reasonably require
  for the purpose of enabling them to pass upon the sale of the Bonds as
  herein contemplated and related proceedings, or in order to evidence the
  accuracy or completeness of any of the representations or warranties, or
  the fulfillment of any of the conditions, herein contained; and all
  proceedings taken by the Company in connection with the sale of the Bonds
  as herein contemplated shall be satisfactory in form and substance to the
  Representatives and counsel for the Underwriters.
 
  If any of the conditions specified in this Section shall not have been
fulfilled when and as required by this Agreement to be fulfilled, this
Agreement and all obligations of the Underwriters hereunder may be cancelled
by the Representatives by notifying the Company of such cancellation in
writing or by telecopy at any time at or prior to the Time of Delivery and any
such cancellation shall be without liability of any party to any other party
except as otherwise provided in this Agreement.
 
  Section 7. Condition of Company's Obligations. The obligations of the
Company to sell and deliver the Bonds are subject to the following conditions:
that at the Time of Delivery no stop order suspending the effectiveness of the
Registration Statement shall have been issued or proceedings therefor
initiated or threatened; that the order of the Illinois Commerce Commission,
referred to in Section 2(k), shall be in full force and effect substantially
in the form in which such order shall originally have been entered; and that
the Indenture shall be qualified under the Trust Indenture Act.
 
  Section 8. Indemnification. (a) The Company agrees to indemnify and hold
harmless each Underwriter and each person, if any, who controls any
Underwriter within the meaning of the Act or the 1934 Act, as follows:
 
    (i) against any and all loss, liability, claim, damage and expense,
  whatsoever, arising out of any untrue statement or alleged untrue statement
  of a material fact contained in the registration statement as it became
  effective, or in any amendment thereto, or in the Registration Statement
  (or any amendment thereto), or the omission or alleged omission therefrom
  of a material fact required to be stated therein or necessary to make the
  statements therein not misleading, or arising out of any untrue statement
  or alleged untrue statement of a material fact contained in any preliminary
  prospectus or the Prospectus (or any amendment or supplement thereto) or
  the omission or alleged omission therefrom of a material fact necessary in
  order to make the statements therein, in light of the circumstances under
  which they were made, not misleading, unless such untrue statement or
  omission or such alleged untrue statement or omission was made in reliance
  upon and in conformity with written information respecting the Underwriters
  furnished to the Company by or on behalf of any Underwriter through the
  Representatives expressly for use in the Registration Statement (or any
  amendment thereto) or the Prospectus (or any amendment or supplement
  thereto);
 
    (ii) against any and all loss, liability, claim, damage and expense
  whatsoever to the extent of the aggregate amount paid in settlement of any
  litigation, commenced or threatened, or of any claim whatsoever based upon
  any such untrue statement or omission or any such alleged untrue statement
  or omission, if such settlement is effected with the written consent of the
  Company; and
 
    (iii) against any and all expenses whatsoever reasonably incurred in
  investigating, preparing or defending against any litigation, commenced or
  threatened, or any claim whatsoever based upon any such untrue statement or
  omission, or any such alleged untrue statement or omission, to the extent
  that any such expense is not paid under (i) or (ii) above, and, in the case
  of (i) above, unless such untrue statement or omission or such alleged
  untrue statement or omission was made in reliance upon and in conformity
  with
 
                                      10
<PAGE>
 
  written information respecting the Underwriters furnished to the Company by
  or on behalf of any Underwriter through the Representatives expressly for
  use in the Registration Statement (or any amendment thereto) or the
  Prospectus (or any amendment or supplement thereto), or, in the case of
  (ii) above, provided such settlement is effected with the written consent
  of the Company.
 
  This indemnity agreement is subject to the condition that, insofar as it
relates to any untrue statement, alleged untrue statement, omission or alleged
omission made in a preliminary prospectus or preliminary prospectus
supplement, but eliminated or remedied in the Prospectus, such indemnity
agreement shall not inure to the benefit of any Underwriter from whom the
person asserting any loss, liability, claim or damage purchases the Bonds
which are the subject thereof (or to the benefit of any person who controls
such Underwriter) if such Underwriter fails to send or give a copy of the
Prospectus (excluding documents incorporated by reference) to such person
prior to or together with written confirmation of the sale of such Bonds to
such person and the delivery thereof would have constituted a defense to the
claim by such person.
 
  In no case shall the Company be liable under this indemnity agreement with
respect to any claim made against any Underwriter or any such controlling
person unless the Company shall be notified in writing of the nature of the
claim within a reasonable time after the assertion thereof, but failure to so
notify the Company shall not relieve it from any liability which it may have
otherwise than on account of this indemnity agreement. The Company shall be
entitled to participate at its own expense in the defense, or, if it so
elects, within a reasonable time after receipt of such notice, to assume the
defense of any suit brought to enforce any such claim, but if it so elects to
assume the defense, such defense shall be conducted by counsel chosen by it
and approved by the Underwriter or Underwriters or controlling person or
persons, defendant or defendants in any suit so brought, which approval shall
not be unreasonably withheld. In the event that the Company elects to assume
the defense of any such suit and retains such counsel, the Underwriter or
Underwriters or controlling person or persons, defendant or defendants in the
suit shall thereafter bear the fees and expense of any additional counsel
retained by them. In the event that the parties to any such action (including
impleaded parties) include both the Company and one or more Underwriters and
any such Underwriter shall have been advised by counsel chosen by it and
satisfactory to the Company that there may be one or more legal defenses
available to it which are different from or additional to those available to
the Company, the Company shall not have the right to assume the defense of
such action on behalf of such Underwriter and will reimburse such Underwriter
and any person controlling such Underwriter as aforesaid for the reasonable
fees and expenses of any counsel retained by them, it being understood that
the Company shall not, in connection with any one action or separate but
similar or related actions in the same jurisdiction arising out of the same
general allegations or circumstances, be liable for the reasonable fees and
expense of more than one separate firm of attorneys for all such Underwriters
and controlling persons, which firm shall be designated in writing by the
Representatives. The Company agrees to notify the Representatives within a
reasonable time of the assertion of any claim against it, any of its officers
or directors or any person who controls the Company within the meaning of the
Act or the 1934 Act, in connection with the sale of the Bonds.
 
  (b) Each Underwriter severally agrees that it will indemnify and hold
harmless the Company, its directors, and each of its officers who signed the
Registration Statement and each person, if any, who controls the Company
within the meaning of the Act or the 1934 Act, to the same extent as the
indemnity contained in subsection (a) of this Section, but only with respect
to statements or omissions made in the registration statement as it became
effective, or in any amendment thereto, or in the Registration Statement (or
any amendment thereto) or the Prospectus (or any amendment or supplement
thereto) in reliance upon and in conformity with written information
respecting the Underwriters furnished to the Company by or on behalf of such
Underwriter through the Representatives expressly for use in the Registration
Statement (or any amendment thereto) or the Prospectus (or any amendment or
supplement thereto). In case any action shall be brought against the Company
or any person so indemnified based on the Registration Statement (or any
amendment thereto) or the Prospectus (or any amendment or supplement thereto)
and in respect of which indemnity may be sought against any Underwriter, such
Underwriter shall have the rights and duties given to the Company, and the
Company and each person so indemnified shall have the rights and duties given
to the Underwriters, by the provisions of subsection (a) of this Section.
 
                                      11
<PAGE>
 
  (c) The obligations of the Company under this Section 8 shall be in addition
to any liability which the Company may otherwise have and shall extend, upon
the same terms and conditions, to each person, if any, who controls any
Underwriter within the meaning of the Act or the 1934 Act; and the obligations
of the Underwriters under this Section 8 shall be in addition to any liability
which the respective Underwriters may otherwise have and shall extend, upon
the same terms and conditions, to each officer and director of the Company and
to each person, if any, who controls the Company within the meaning of the Act
or the 1934 Act.
 
  Section 9. Representations, Warranties and Agreements to Survive Delivery.
All representations, warranties and agreements contained in the Underwriting
Agreement and/or contained in certificates of officers of the Company
submitted pursuant hereto, shall remain operative and in full force and
effect, regardless of any investigation made by or on behalf of any
Underwriter or any controlling person of any Underwriter, or by or on behalf
of the Company, and shall survive payment for and delivery of the Bonds.
 
  Section 10. Effective Date of the Underwriting Agreement and Termination
Thereof. (a) The Underwriting Agreement shall become effective at the time of
the initial public offering by the Underwriters of any of the Bonds. The time
of the initial public offering shall mean 12:00 noon, New York City time, on
the first full business day after the Underwriting Agreement is executed or at
such time as the Representatives may authorize the sale of the Bonds to the
public by the Underwriters or other securities dealers, whichever shall first
occur. The Representatives or the Company may prevent the Underwriting
Agreement from becoming effective without liability of any party to any other
party, except as otherwise provided in the Underwriting Agreement, by giving
the notice indicated below in this Section prior to the time the Underwriting
Agreement would otherwise become effective as herein provided.
 
  (b) The Representatives shall have the right to terminate the Underwriting
Agreement by giving the notice indicated below in this Section at any time at
or prior to the Time of Delivery if (i) the Company shall have sustained since
the respective dates as of which information is given in the Prospectus any
material loss or interference with its business from fire, explosion, flood or
other calamity, whether or not covered by insurance, or from any labor dispute
or court or governmental action, order or decree; or (ii) since the respective
dates as of which information is given in the Prospectus there shall have been
any material increase in the long-term debt, or any material adverse change,
or any development involving a prospective material adverse change, in or
affecting the general business affairs, management, financial position,
results of operations, or business prospects of the Company and its
subsidiaries considered as one enterprise, otherwise than as set forth or
contemplated in the Prospectus, the effect of which, in any such case
described in clause (i) or (ii), in the judgment of the Representatives makes
it impracticable or inadvisable to proceed with the public offering or the
delivery of the Bonds on the terms and in the manner contemplated in the
Prospectus; or (iii) there shall have occurred the outbreak or escalation of
hostilities involving in a significant way the armed forces of the United
States, or the declaration by the United States, on or after the date of the
Underwriting Agreement, of a national emergency or war, or there shall have
occurred a general suspension or limitation of trading in securities on the
New York or American Stock Exchanges, or the establishment of minimum prices
on either such Exchange, or a general moratorium on commercial banking
activities in New York is declared by either federal or New York state
authorities, the effect of which in the judgment of the Representatives makes
it impracticable or inadvisable to proceed with the public offering or the
delivery of the Bonds on the terms and in the manner contemplated in the
Prospectus. If the Representatives shall so terminate the Underwriting
Agreement, such termination shall be without liability of any party to any
other party except as otherwise provided in the Underwriting Agreement.
 
  (c) If the Representatives elect to prevent the Underwriting Agreement from
becoming effective or to terminate the Underwriting Agreement as provided in
this Section, the Company and each other Underwriter shall be notified
promptly by the Representatives, by telephone or telegram, confirmed by
letter. If the Company elects to prevent the Underwriting Agreement from
becoming effective as provided in this Section, the Representatives shall be
notified promptly by the Company by telephone or telegram, confirmed by
letter.
 
  Section 11. Default of Underwriters. If any one or more of the Underwriters
shall fail at the Time of Delivery to purchase the amount of Bonds which it or
they are obligated to purchase hereunder (the "Defaulted
 
                                      12
<PAGE>
 
Bonds"), then the Representatives shall have the right, within 24 hours
thereafter, to make arrangements for one or more of the non-defaulting
Underwriters, or any other underwriters, to purchase all, but not less than
all, of the Defaulted Bonds in such amounts as may be agreed upon and upon the
terms herein set forth. If, however, during such 24 hours the Representatives
shall not have completed such arrangements for the purchase of all of the
Defaulted Bonds, then the Company shall be entitled to a further period of 24
hours within which to procure another party or parties satisfactory to the
Representatives to purchase all of such Defaulted Bonds on such terms. If,
after giving effect to any arrangements for the purchase of Defaulted Bonds by
the Representatives and the Company as provided above, then:
 
    (a) if the amount of Defaulted Bonds does not exceed 10% of the aggregate
  principal amount of the Bonds being sold hereunder, the non-defaulting
  Underwriters shall be obligated to purchase severally the full amount
  thereof in the proportions that their respective underwriting obligations
  hereunder bear to the underwriting obligations of all non-defaulting
  Underwriters, or
 
    (b) if the amount of Defaulted Bonds exceeds 10% of the aggregate
  principal amount of the Bonds being sold hereunder, the Underwriting
  Agreement shall terminate without any liability on the part of the Company
  or any non-defaulting Underwriter.
 
  The termination of the Underwriting Agreement pursuant to this Section shall
be without liability on the part of the Company or any of said non-defaulting
Underwriters, except for the respective obligations of the Company and the
Underwriters pursuant to Section 8 and except that the Company shall be
obligated to reimburse the Underwriters for their out-of-pocket expenses
(including reasonable fees and disbursements of counsel for the Underwriters)
incurred in connection with the offering if the Underwriting Agreement could
have been terminated by the Representatives pursuant to Section 6 or 10(b).
 
  Nothing herein shall relieve any Underwriter so defaulting from liability,
if any, for such default.
 
  In the event of a default by any one or more Underwriters as set forth in
this Section, either the Representatives or the Company shall have the right
to postpone the Time of Delivery for an additional period not exceeding 7 days
in order that any required changes in the Registration Statement and
Prospectus or in any other documents or arrangements may be effected.
 
  Section 12. Notices. Except as otherwise provided in the Underwriting
Agreement, all communications under the Underwriting Agreement shall be in
writing, and, if sent to the Underwriters, shall be mailed, delivered or
telecopied and confirmed to the address of the Representatives, as set forth
in the Underwriting Agreement (except that any notice to an Underwriter
pursuant to Section 8 hereof shall be sent to it at its address set forth in
the copies of the Underwriters' Questionnaires furnished to the Company), or,
if sent to the Company shall be mailed or telecopied and confirmed to it at
P.O. Box 190, Aurora, Illinois 60507-0190, or delivered to it at 1844 Ferry
Road, Naperville, Illinois, for the attention of Donald W. Lohrentz, Vice
President and Treasurer.
 
  Section 13. Parties. The Underwriting Agreement shall inure to the benefit
of and be binding upon the Underwriters and the Company and their respective
successors. Nothing expressed or mentioned in the Underwriting Agreement is
intended or shall be construed to give any person, firm or corporation, other
than the parties hereto and their respective successors and the controlling
persons and the directors and officers referred to in Section 8, any legal or
equitable right, remedy or claim under or in respect of the Underwriting
Agreement or any provision herein contained; the Underwriting Agreement and
all conditions and provisions hereof being intended to be and being for the
sole and exclusive benefit of the parties hereto and their respective
successors and said controlling persons, directors and officers and for the
benefit of no other person, firm or corporation. No purchaser of any Bonds
from any Underwriter shall be deemed to be a successor by reason merely of
such purchase.
 
  Section 14. Choice of Law. The Underwriting Agreement shall be construed in
accordance with, and governed by, the laws of the State of Illinois.
 
                                      13


<PAGE>
                                                                  Nicor Gas
                                                                  Form 10-Q
                                                                  Exhibit 4.01



                            SUPPLEMENTAL INDENTURE
 
                                --------------
 
                            DATED OCTOBER 15, 1997
 
                                --------------
 
                         NORTHERN ILLINOIS GAS COMPANY
 
                                      TO
 
                         HARRIS TRUST AND SAVINGS BANK
 
                      TRUSTEE UNDER INDENTURE DATED AS OF
                       JANUARY 1, 1954 AND SUPPLEMENTAL
                              INDENTURES THERETO
 
                                --------------
 
                             FIRST MORTGAGE BONDS
                      7 3/8% SERIES DUE OCTOBER 15, 2027
 
This instrument was prepared by Donald W. Lohrentz, 1844 Ferry Road, Naper-
ville, Illinois 60563-9600.
 
Return to: Northern Illinois Gas Company
Attn: Joe R. Johnson
P.O. Box 190, Aurora, IL 60507-0190
<PAGE>
 
This Supplemental Indenture, dated the fifteenth day of October, 1997, between
  Northern Illinois Gas Company, a corporation organized and existing under
  the laws of the State of Illinois (hereinafter called the "Company"), and
  Harris Trust and Savings Bank, an Illinois banking corporation (hereinafter
  called the "Trustee"), as Trustee under an Indenture dated as of January 1,
  1954, as supplemented by Supplemental Indentures dated, respectively, Febru-
  ary 9, 1954, April 1, 1956, June 1, 1959, July 1, 1960, June 1, 1963, July
  1, 1963, August 1, 1964, August 1, 1965, May 1, 1966, August 1, 1966, July
  1, 1967, June 1, 1968, December 1, 1969, August 1, 1970, June 1, 1971, July
  1, 1972, July 1, 1973, April 1, 1975, April 30, 1976, April 30, 1976, July
  1, 1976, August 1, 1976, December 1, 1977, January 15, 1979, December 1,
  1981, March 1, 1983, October 1, 1984, December 1, 1986, March 15, 1988, July
  1, 1988, July 1, 1989, July 15, 1990, August 15, 1991, July 15, 1992, Febru-
  ary 1, 1993, March 15, 1993, May 1, 1993, July 1, 1993, August 15, 1994, Oc-
  tober 15, 1995, May 10, 1996, August 1, 1996 and June 1, 1997, such Inden-
  ture dated as of January 1, 1954, as so supplemented, being hereinafter
  called the "Indenture."
 
Witnesseth:
 
 Whereas, the Indenture provides for the issuance from time to time thereun-
der, in series, of bonds of the Company for the purposes and subject to the
limitations therein specified; and
 
 Whereas, the Company desires, by this Supplemental Indenture, to create an
additional series of bonds to be issuable under the Indenture, such bonds to
be designated "First Mortgage Bonds, 7 3/8% Series due October 15, 2027"
(hereinafter called the "bonds of this Series"), and the terms and provisions
to be contained in the bonds of this Series or to be otherwise applicable
thereto to be as set forth in this Supplemental Indenture; and
 
 Whereas, the forms, respectively, of the bonds of this Series, and Trustee's
certificate to be endorsed on all bonds of this Series, are to be substan-
tially as follows:
 
                            (FORM OF FACE OF BOND)
 
No. RU _______                                                               $
 
                         NORTHERN ILLINOIS GAS COMPANY
 
            First Mortgage Bond, 7 3/8% Series due October 15, 2027
<PAGE>
 
 Northern Illinois Gas Company, an Illinois corporation (hereinafter called
the "Company"), for value received, hereby promises to pay to            or
registered assigns, the sum of             Dollars, on the fifteenth day of
October, 2027, and to pay to the registered owner hereof interest on said sum
from the date hereof until said sum shall be paid, at the rate of seven and
three-eighths per centum (7 3/8%) per annum, payable semiannually on the fif-
teenth day of April and the fifteenth day of October in each year. Both the
principal of and the interest on this bond shall be payable at the office or
agency of the Company in the City of Chicago, State of Illinois, or, at the
option of the registered owner, at the office or agency of the Company in the
Borough of Manhattan, The City and State of New York, in any coin or currency
of the United States of America which at the time of payment is legal tender
for the payment of public and private debts. Any installment of interest on
the bonds may, at the Company's option, be paid by mailing checks for such in-
terest payable to or upon the written order of the person entitled thereto to
the address of such person as it appears on the registration books.
 
 So long as there is no existing default in the payment of interest on this
bond, the interest so payable on any interest payment date will be paid to the
person in whose name this bond is registered on the April 1 or the October 1
(whether or not a business day), as the case may be, next preceding such in-
terest payment date. If and to the extent that the Company shall default in
the payment of interest due on such interest payment date, such defaulted in-
terest shall be paid to the person in whose name this bond is registered on
the record date fixed, in advance, by the Company for the payment of such de-
faulted interest.
 
 Additional provisions of this bond are set forth on the reverse hereof.
 
 This bond shall not be entitled to any security or benefit under the Inden-
ture or be valid or become obligatory for any purpose unless and until it
shall have been authenticated by the execution by the Trustee, or its succes-
sor in trust under the Indenture, of the certificate endorsed hereon.
 
 In witness whereof, Northern Illinois Gas Company has caused this bond to be
executed in its name by its Chairman, President, or a Vice President, manually
or by facsimile signature, and has caused its corporate seal to be impressed
 
                                       2
<PAGE>
 
hereon or a facsimile thereof to be imprinted hereon and to be attested by its
Secretary or its Assistant Secretary, manually or by facsimile signature.
 
Dated___________
 
                                   Northern Illinois Gas Company
 
                                   By _________________________________________
                                                      President
 
Attest:
 
- -----------------------------------
             Secretary
 
               (form of trustee's certificate of authentication)
 
 This bond is one of the bonds of the series designated therein, referred to
and described in the within-mentioned Supplemental Indenture dated October 15,
1997.
 
Harris Trust and Savings Bank,
  Trustee
 
By ________________________________
         Authorized Officer
 
                        (form of reverse side of bond)
 
 This bond is one, of the series hereinafter specified, of the bonds issued
and to be issued in series from time to time under and in accordance with and
secured by an Indenture dated as of January 1, 1954, to Harris Trust and Sav-
ings Bank, as Trustee, as supplemented by certain indentures supplemental
thereto, executed and delivered to the Trustee; and this bond is one of a se-
ries of such bonds, designated "Northern Illinois Gas Company First Mortgage
Bonds, 7 3/8% Series due October 15, 2027" (herein called "bonds of this Se-
ries"), the issuance of which is provided for by a Supplemental Indenture
dated October 15, 1997 (hereinafter called the "Supplemental Indenture"), exe-
cuted and delivered by the Company to the Trustee. The term "Indenture", as
hereinafter used, means said Indenture dated as of January 1, 1954, and all
indentures supplemental thereto from time to time in effect. Reference is made
to the Indenture for a description of the property mortgaged and pledged, the
nature and extent of the
 
                                       3
<PAGE>
 
security, the rights of the holders and registered owners of said bonds, of
the Company and of the Trustee in respect of the security, and the terms and
conditions governing the issuance and security of said bonds.
 
 With the consent of the Company and to the extent permitted by and as pro-
vided in the Indenture, modifications or alterations of the Indenture or of
any supplemental indenture and of the rights and obligations of the Company
and of the holders and registered owners of the bonds may be made, and compli-
ance with any provision of the Indenture or of any supplemental indenture may
be waived, by the affirmative vote of the holders and registered owners of not
less than sixty-six and two-thirds per centum (66 2/3%) in principal amount of
the bonds then outstanding under the Indenture, and by the affirmative vote of
the holders and registered owners of not less than sixty-six and two-thirds
per centum (66 2/3%) in principal amount of the bonds of any series then out-
standing under the Indenture and affected by such modification or alteration,
in case one or more but less than all of the series of bonds then outstanding
under the Indenture are so affected, but in any case excluding bonds disquali-
fied from voting by reason of the Company's interest therein as provided in
the Indenture; subject, however, to the condition, among other conditions
stated in the Indenture, that no such modification or alteration shall be made
which, among other things, will permit the extension of the time or times of
payment of the principal of or the interest or the premium, if any, on this
bond, or the reduction in the principal amount hereof or in the rate of inter-
est or the amount of any premium hereon, or any other modification in the
terms of payment of such principal, interest or premium, which terms of pay-
ment are unconditional, or, otherwise than as permitted by the Indenture, the
creation of any lien ranking prior to or on a parity with the lien of the In-
denture with respect to any of the mortgaged property, all as more fully pro-
vided in the Indenture.
 
  The bonds of this Series may not be called for redemption by the Company
prior to October 15, 2002. On October 15, 2002 and thereafter until maturity
on October 15, 2027, upon the notice hereinafter stated and in the manner and
with the effect provided in the Indenture, the bonds of this Series are re-
deemable at the option of the Company, as a whole at any time or in part from
time to time, at the following redemption prices (expressed as percentages of
principal amount) set forth under "General Redemption Prices", plus accrued
and unpaid interest to the redemption date:
 
                                       4
<PAGE>
 
                           GENERAL REDEMPTION PRICES
                      -----------------------------------
                       IF REDEEMED DURING TWELVE MONTHS'
                         PERIOD BEGINNING OCTOBER 15:
                      -----------------------------------
 
      (THE YEARS AND THE PERCENTAGES OF PRINCIPAL AMOUNT SET FORTH UNDER
         "GENERAL REDEMPTION PRICES" IN SECTION 4 OF ARTICLE I OF THIS
               SUPPLEMENTAL INDENTURE ARE TO BE INSERTED HERE.)
 
 Notice of each redemption shall be mailed to all registered owners not less
than thirty nor more than forty-five days before the redemption date.
 
 In case of certain completed defaults specified in the Indenture, the princi-
pal of this bond may be declared or may become due and payable in the manner
and with the effect provided in the Indenture.
 
 No recourse shall be had for the payment of the principal of or the interest
or the premium, if any, on this bond, or for any claim based hereon, or other-
wise in respect hereof or of the Indenture, to or against any incorporator,
stockholder, officer or director, past, present or future, of the Company or
of any predecessor or successor corporation, either directly or through the
Company or such predecessor or successor corporation, under any constitution
or statute or rule of law, or by the enforcement of any assessment or penalty,
or otherwise, all such liability of incorporators, stockholders, directors and
officers being waived and released by the registered owner hereof by the ac-
ceptance of this bond and being likewise waived and released by the terms of
the Indenture, all as more fully provided therein.
 
  This bond is transferable by the registered owner hereof, in person or by
duly authorized attorney, at the office or agency of the Company in the City
of Chicago, State of Illinois, or, at the option of the registered owner, at
the office or agency of the Company in the Borough of Manhattan, The City and
State of New York, upon surrender and cancellation of this bond; and thereupon
a new registered bond or bonds without coupons of the same aggregate principal
amount and series will, upon the payment of any transfer tax or taxes payable,
be issued to the transferee in exchange herefor. The Company shall not be re-
quired to exchange or transfer this bond if this bond or a portion hereof has
been selected for redemption.
 
                              (end of bond form)
 
and
 
                                       5
<PAGE>
 
 Whereas, all acts and things necessary to make this Supplemental Indenture,
when duly executed and delivered, a valid, binding and legal instrument in ac-
cordance with its terms and for the purposes herein expressed, have been done
and performed, and the execution and delivery of this Supplemental Indenture
have in all respects been duly authorized;
 
 Now, Therefore, in consideration of the premises and of the sum of one dollar
paid by the Trustee to the Company, and for other good and valuable considera-
tions, the receipt of which is hereby acknowledged, for the purpose of secur-
ing the due and punctual payment of the principal of and the interest and pre-
mium, if any, on all bonds which shall be issued under the Indenture, and for
the purpose of securing the faithful performance and observance of all the
covenants and conditions set forth in the Indenture and in all indentures sup-
plemental thereto, the Company by these presents does grant, bargain, sell,
transfer, assign, pledge, mortgage, warrant and convey unto Harris Trust and
Savings Bank, as Trustee, and its successor or successors in the trust hereby
created, all property, real and personal (other than property expressly ex-
cepted from the lien and operation of the Indenture), which, at the actual
date of execution and delivery of this Supplemental Indenture, is solely used
or held for use in the operation by the Company of its gas utility system and
in the conduct of its gas utility business and all property, real and person-
al, used or useful in the gas utility business (other than property expressly
excepted from the lien and operation of the Indenture) acquired by the Company
after the actual date of execution and delivery of this Supplemental Indenture
or (subject to the provisions of Section 16.03 of the Indenture) by any suc-
cessor corporation after such execution and delivery, and it is further agreed
by and between the Company and the Trustee as follows:
 
                                   ARTICLE I
 
                             Bonds of this Series
 
 Section 1. The bonds of this Series shall, as hereinbefore recited, be desig-
nated as the Company's "First Mortgage Bonds, 7 3/8% Series due October 15,
2027." The bonds of this Series which may be issued and outstanding shall not
exceed $50,000,000 in aggregate principal amount, exclusive of bonds of such
series authenticated and delivered pursuant to the provisions of Section 4.12
of the Indenture.
 
 Section 2. The bonds of this Series shall be registered bonds without cou-
pons, and the form of such bonds, and of the Trustee's certificate of authen-
tication to
 
                                       6
<PAGE>
 
be endorsed on all bonds of this Series, shall be substantially as hereinbe-
fore recited, respectively.
 
 Section 3. The bonds of this Series shall be issued in the denomination of
$1,000 each and in such multiple or multiples thereof as shall be determined
and authorized by the Board of Directors of the Company or by any officer or
officers of the Company authorized by the Board of Directors to make such de-
termination, the authorization of the denomination of any bond to be conclu-
sively evidenced by the execution thereof on behalf of the Company. The bonds
of this Series shall be numbered, RU-1 and consecutively upwards, or in such
other appropriate manner as shall be determined and authorized by the Board of
Directors of the Company.
 
 All bonds of this Series shall be dated October 15, 1997, except that each
bond issued on or after the first payment of interest thereon shall be dated
as of the date of the interest payment date thereof to which interest shall
have been paid on the bonds of such series next preceding the date of issue,
unless issued on an interest payment date to which interest shall have been so
paid, in which event such bonds shall be dated as of the date of issue; pro-
vided, however, that bonds issued on or after April 1 and before the next suc-
ceeding April 15 or on or after October 1 and before the next succeeding Octo-
ber 15 shall be dated the next succeeding interest payment date if interest
shall have been paid to such date. All bonds of this Series shall mature Octo-
ber 15, 2027, and shall bear interest at the rate of 7 3/8% per annum until
the principal thereof shall be paid. Such interest shall be calculated on the
basis of a 360-day year consisting of twelve 30-day months and shall be pay-
able semiannually on the fifteenth day of April and the fifteenth day of Octo-
ber in each year. So long as there is no existing default in the payment of
interest on the bonds of this Series, such interest shall be payable to the
person in whose name each such bond is registered on the April 1 and October 1
(whether or not a business day), as the case may be, next preceding the re-
spective interest payment dates; provided, however, if and to the extent that
the Company shall default in the payment of interest due on such interest pay-
ment date, such defaulted interest shall be paid to the person in whose name
each such bond is registered on the record date fixed, in advance, by the Com-
pany for the payment of such defaulted interest.
 
 The principal of and interest and premium, if any, on the bonds of this Se-
ries shall be payable in any coin or currency of the United States of America
which at the time of payment is legal tender for the payment of public and
private debts,
 
                                       7
<PAGE>
 
and shall be payable at the office or agency of the Company in the City of
Chicago, State of Illinois, or, at the option of the registered owner, at the
office or agency of the Company in the Borough of Manhattan, The City and
State of New York. Any installment of interest on the bonds may, at the
Company's option, be paid by mailing checks for such interest payable to or
upon the written order of the person entitled thereto to the address of such
person as it appears on the registration books. The bonds of this Series shall
be registrable, transferable and exchangeable in the manner provided in Sec-
tions 4.08 and 4.09 of the Indenture, at either of such offices or agencies.
 
 Section 4. The bonds of this Series may not be called for redemption by the
Company prior to October 15, 2002. On October 15, 2002 and thereafter until
maturity on October 15, 2027, the bonds of this Series, upon the mailing of
notice and in the manner provided in Section 7.01 of the Indenture (except
that no published notice shall be required for the bonds of this Series), and
with the effect provided in Section 7.02 thereof, shall be redeemable at the
option of the Company, as a whole at any time or in part from time to time, at
the following redemption prices (expressed as percentages of principal amount)
set forth below under "General Redemption Prices," plus accrued and unpaid in-
terest to the redemption date:
 
                           GENERAL REDEMPTION PRICES
                      -----------------------------------
                       IF REDEEMED DURING TWELVE MONTHS'
                         PERIOD BEGINNING OCTOBER 15:
                      -----------------------------------
 
<TABLE>
<CAPTION>
        YEAR               PERCENTAGE                         YEAR                         PERCENTAGE
        ----               ----------                         ----                         ----------
        <S>                <C>                                <C>                          <C>
        2002                105.16%                           2014                          101.04%
        2003                104.82                            2015                          100.69
        2004                104.47                            2016                          100.35
        2005                104.13                            2017                          100.00
        2006                103.79                            2018                          100.00
        2007                103.44                            2019                          100.00
        2008                103.10                            2020                          100.00
        2009                102.75                            2021                          100.00
        2010                102.41                            2022                          100.00
        2011                102.07                            2023                          100.00
        2012                101.72                            2024                          100.00
        2013                101.38                            2025                          100.00
                                                              2026                          100.00
</TABLE>
 
 Section 5. No sinking fund is to be provided for the bonds of this Series.
 
                                       8
<PAGE>
 
                                  ARTICLE II
 
                           Miscellaneous Provisions
 
 Section 1. This Supplemental Indenture is executed by the Company and the
Trustee pursuant to provisions of Section 4.02 of the Indenture and the terms
and conditions hereof shall be deemed to be a part of the terms and conditions
of the Indenture for any and all purposes. The Indenture, as heretofore sup-
plemented and as supplemented by this Supplemental Indenture, is in all re-
spects ratified and confirmed.
 
 Section 2. This Supplemental Indenture shall bind and, subject to the provi-
sions of Article XVI of the Indenture, inure to the benefit of the respective
successors and assigns of the parties hereto.
 
 Section 3. Although this Supplemental Indenture is dated October 15, 1997, it
shall be effective only from and after the actual time of its execution and
delivery by the Company and the Trustee on the date indicated by their respec-
tive acknowledgments hereto annexed.
 
 Section 4. This Supplemental Indenture may be simultaneously executed in any
number of counterparts, and all such counterparts executed and delivered, each
as an original, shall constitute but one and the same instrument.
 
                                       9
<PAGE>
 
 In Witness Whereof, Northern Illinois Gas Company has caused this Supplemen-
tal Indenture to be executed in its name by its President, a Senior Vice Pres-
ident, or Treasurer, and its corporate seal to be hereunto affixed and at-
tested by its Secretary or its Assistant Secretary, and Harris Trust and Sav-
ings Bank, as Trustee under the Indenture, has caused this Supplemental Inden-
ture to be executed in its name by one of its Vice Presidents, and its seal to
be hereunto affixed and attested by its Assistant Secretary, all as of the day
and year first above written.
 
Northern Illinois Gas Company
 
By ________________________________
       Senior Vice President
 
                                   Attest:
 
                                   --------------------------------------------
                                               Assistant Secretary
 
Harris Trust and Savings Bank,
 as Trustee
 
By ________________________________
           Vice President
 
                                   Attest:
 
                                   --------------------------------------------
                                               Assistant Secretary
 
                                      10
<PAGE>
 
State of Illinois }  ss:
County of DuPage
 
 I, Catherine A. Gengler, Notary Public in the State aforesaid, Do Hereby Cer-
tify that David L. Cyranoski, Senior Vice President of Northern Illinois Gas
Company, an Illinois corporation, one of the parties described in and which
executed the foregoing instrument, and Alexander C. Allison, Assistant Secre-
tary of said corporation, who are both personally known to me to be the same
persons whose names are subscribed to the foregoing instrument as such Senior
Vice President and Assistant Secretary, respectively, and who are both person-
ally known to me to be the Senior Vice President and the Assistant Secretary,
respectively, of said corporation, appeared before me this day in person and
severally acknowledged that they signed, sealed, executed and delivered said
instrument as their free and voluntary act as such Senior Vice President and
Assistant Secretary, respectively, of said corporation, and as the free and
voluntary act of said corporation, for the uses and purposes therein set
forth.
 
 Given under my hand and notarial seal this 24th day of October A.D. 1997.
 
                                   --------------------------------------------
                                                  Notary Public
 
My Commission expires August 1, 2001.
 
                                      11
<PAGE>
 
State of Illinois } ss:
County of Cook
 
 I, Kimberley Lange, a Notary Public in and for said County, in the State
aforesaid, Do Hereby Certify that J. Bartolini, Vice President of Harris Trust
and Savings Bank, an Illinois banking corporation, one of the parties de-
scribed in and which executed the foregoing instrument, and D. G. Donovan, As-
sistant Secretary of said banking corporation, who are both personally known
to me to be the same persons whose names are subscribed to the foregoing in-
strument as such Vice President and Assistant Secretary, respectively, and who
are both personally known to me to be a Vice President and an Assistant Secre-
tary, respectively, of said banking corporation, appeared before me this day
in person and severally acknowledged that they signed, sealed, executed and
delivered said instrument as their free and voluntary act as such Vice Presi-
dent and Assistant Secretary, respectively, of said banking corporation, and
as the free and voluntary act of said banking corporation, for the uses and
purposes therein set forth.
 
 Given under my hand and notarial seal this 24th day of October A.D. 1997.
 
                                   --------------------------------------------
                                                  Notary Public
 
My Commission expires December 14, 1997.
 
                                      12
<PAGE>
 
                                RECORDING DATA
 
 This Supplemental Indenture was recorded on October 27 or 28, 1997, in the
office of the Recorder of Deeds in certain counties in the State of Illinois,
as follows:
 
<TABLE>
<CAPTION>
     COUNTY                  BOOK                           PAGE                           DOCUMENT NO.
     ------                  ----                           ----                           ------------
   <S>                       <C>                            <C>                            <C>
   Adams
   Boone
   Bureau
   Carroll
   Champaign
   Cook
   DeKalb
   DeWitt
   DuPage
   Ford
   Grundy
   Hancock
   Henderson
   Henry
   Iroquois
   Jo Daviess
   Kane
   Kankakee
   Kendall
   Lake
   La Salle
   Lee
   Livingston
   McHenry
   McLean
   Mercer
   Ogle
   Piatt
   Pike
   Rock Island
   Stephenson
   Tazewell
   Vermilion
   Whiteside
   Will
   Winnebago
   Woodford
</TABLE>
 
                                      13


<TABLE>
                                                                             
                                                                                              Nicor Gas        
                                                                                              Form 10-Q
                                                                                              Exhibit 12.01


                                                  NICOR GAS
                       COMPUTATION OF CONSOLIDATED RATIO OF EARNINGS TO FIXED CHARGES
                                                 (Thousands)
<CAPTION>

                                             Twelve
                                          Months Ended
                                          September 30                  Year Ended December 31                 
                                              1997        1996      1995       1994       1993      1992   

Earnings available to cover fixed charges:

  <S>                                     <C>          <C>       <C>        <C>        <C>       <C>
  Net income                              $ 105,217    $ 107,106 $  85,448  $  93,078  $  94,935 $  91,239

  Add:  Income taxes                         62,685       63,579    49,881     50,958     52,890    49,578

        Fixed charges                        46,851       46,747    39,400     37,729     40,960    41,648

        Allowance for funds used
          during construction                   (14)          (5)     (911)      (151)       (64)     (915)

  Total                                   $ 214,739    $ 217,427 $ 173,818  $ 181,614  $ 188,721 $ 181,550


Fixed charges:

  Interest on debt                        $  45,385    $  43,762 $  38,129  $  36,726  $  38,949 $  39,773

  Other interest charges and
    amortization of debt discount,
    premium and expense, net                  1,466        2,985     1,271      1,003      2,011     1,875

  Total                                   $  46,851    $  46,747 $  39,400  $  37,729  $  40,960 $  41,648


Ratio of earnings to fixed charges             4.58         4.65      4.41       4.81       4.61      4.36
</TABLE>



<TABLE> <S> <C>

<ARTICLE> UT
<LEGEND>
THIS SCHEDULE CONTAINS SUMMARY FINANCIAL INFORMATION EXTRACTED FROM THE
CONSOLIDATED STATEMENT OF INCOME, THE CONSOLIDATED BALANCE SHEET AND THE
CONSOLIDATED STATEMENT OF CASH FLOWS AND IS QUALIFIED IN ITS ENTIRETY BY
REFERENCE TO SUCH FINANCIAL STATEMENTS.
</LEGEND>
<MULTIPLIER> 1,000,000
       
<S>                             <C>
<PERIOD-TYPE>                   9-MOS
<FISCAL-YEAR-END>                          DEC-31-1996
<PERIOD-END>                               SEP-30-1997
<BOOK-VALUE>                                  PER-BOOK
<TOTAL-NET-UTILITY-PLANT>                        1,645
<OTHER-PROPERTY-AND-INVEST>                          7
<TOTAL-CURRENT-ASSETS>                             300
<TOTAL-DEFERRED-CHARGES>                             0
<OTHER-ASSETS>                                      77
<TOTAL-ASSETS>                                   2,029
<COMMON>                                            76
<CAPITAL-SURPLUS-PAID-IN>                          108
<RETAINED-EARNINGS>                                497
<TOTAL-COMMON-STOCKHOLDERS-EQ>                     681
                                9
                                          1
<LONG-TERM-DEBT-NET>                               521
<SHORT-TERM-NOTES>                                   0
<LONG-TERM-NOTES-PAYABLE>                            0
<COMMERCIAL-PAPER-OBLIGATIONS>                     108  
<LONG-TERM-DEBT-CURRENT-PORT>                       25
                            1
<CAPITAL-LEASE-OBLIGATIONS>                          0
<LEASES-CURRENT>                                     0
<OTHER-ITEMS-CAPITAL-AND-LIAB>                     683
<TOT-CAPITALIZATION-AND-LIAB>                    2,029
<GROSS-OPERATING-REVENUE>                        1,215
<INCOME-TAX-EXPENSE>                                44
<OTHER-OPERATING-EXPENSES>                       1,064
<TOTAL-OPERATING-EXPENSES>                       1,108
<OPERATING-INCOME-LOSS>                            107
<OTHER-INCOME-NET>                                   2
<INCOME-BEFORE-INTEREST-EXPEN>                     109
<TOTAL-INTEREST-EXPENSE>                            34
<NET-INCOME>                                        75
                          1
<EARNINGS-AVAILABLE-FOR-COMM>                       74
<COMMON-STOCK-DIVIDENDS>                            76
<TOTAL-INTEREST-ON-BONDS>                            0
<CASH-FLOW-OPERATIONS>                             299
<EPS-PRIMARY>                                        0
<EPS-DILUTED>                                        0<F1>
<FN>
<F1>NICOR GAS IS A WHOLLY OWNED SUBSIDIARY OF NICOR INC.  EARNINGS PER SHARE
INFORMAION IS THEREFORE OMITTED.
</FN>
        


</TABLE>


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