Exhibit 4(a)

                        TEXAS UTILITIES ELECTRIC COMPANY

                                       TO

                              THE BANK OF NEW YORK,
                         (formerly Irving Trust Company)


                         Trustee under the Texas Utilities
                         Electric Company Mortgage and
                         Deed of Trust, dated as of
                         December 1, 1983

                               ------------------


                       Fifty-ninth Supplemental Indenture

                        Providing among other things for
                              First Mortgage Bonds,
                           Pollution Control Series AK








                               ------------------

                            Dated as of March 1, 1999



             This Instrument Grants a Security Interest by a Utility
           This Instrument Contains After-Acquired Property Provisions

<PAGE>
<PAGE>



             This Instrument Grants a Security Interest by a Utility
           This Instrument Contains After-Acquired Property Provisions

                       FIFTY-NINTH SUPPLEMENTAL INDENTURE

                        ---------------------------------

     INDENTURE, dated as of March 1, 1999, between TEXAS UTILITIES ELECTRIC
COMPANY, a corporation of the State of Texas, whose address is Energy Plaza,
1601 Bryan Street, Dallas, Texas 75201 (hereinafter sometimes called the
Company), and THE BANK OF NEW YORK (formerly Irving Trust Company), a
corporation of the State of New York, whose address is 101 Barclay Street, New
York, New York 10286 (hereinafter sometimes called the Trustee), Trustee under
the Mortgage and Deed of Trust, dated as of December 1, 1983 (hereinafter called
the Original Indenture, the Original Indenture and any and all indentures and
instruments supplemental thereto being hereinafter sometimes collectively called
the Mortgage), which Original Indenture was executed and delivered by the
Company to secure the payment of bonds issued or to be issued under and in
accordance with the provisions of the Mortgage, reference to which Mortgage is
made, this Indenture (hereinafter called the Fifty-ninth Supplemental Indenture)
being supplemental thereto;

     WHEREAS, said Original Indenture was recorded or filed as required in the
State of Texas; and

     WHEREAS, the Company executed and delivered to the Trustee the following
supplemental indentures:

                         Designation                         Dated as of
                         -----------                         -----------

First Supplemental Indenture..............................   April 1, 1984
Second Supplemental Indenture.............................   September 1, 1984
Third Supplemental Indenture..............................   April 1, 1985
Fourth Supplemental Indenture.............................   August 1, 1985
Fifth Supplemental Indenture..............................   September 1, 1985
Sixth Supplemental Indenture..............................   December 1, 1985
Seventh Supplemental Indenture............................   March 1, 1986
Eighth Supplemental Indenture.............................   May 1, 1986
Ninth Supplemental Indenture..............................   October 1, 1986
Tenth Supplemental Indenture..............................   December 1, 1986
Eleventh Supplemental Indenture...........................   December 1, 1986
Twelfth Supplemental Indenture............................   February 1, 1987
Thirteenth Supplemental Indenture.........................   March 1, 1987
Fourteenth Supplemental Indenture.........................   April 1, 1987
Fifteenth Supplemental Indenture..........................   July 1, 1987
Sixteenth Supplemental Indenture..........................   September 1, 1987
Seventeenth Supplemental Indenture........................   October 1, 1987
Eighteenth Supplemental Indenture.........................   March 1, 1988
Nineteenth Supplemental Indenture.........................   May 1, 1988

                                  2
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                         Designation                         Dated as of
                         -----------                         -----------

Twentieth Supplemental Indenture..........................   September 1, 1988
Twenty-first Supplemental Indenture.......................   November 1, 1988
Twenty-second Supplemental Indenture......................   January 1, 1989
Twenty-third Supplemental Indenture.......................   August 1, 1989
Twenty-fourth Supplemental Indenture......................   November 1, 1989
Twenty-fifth Supplemental Indenture.......................   December 1, 1989
Twenty-sixth Supplemental Indenture.......................   February 1, 1990
Twenty-seventh Supplemental Indenture.....................   September 1, 1990
Twenty-eighth Supplemental Indenture......................   October 1, 1990
Twenty-ninth Supplemental Indenture.......................   October 1, 1990
Thirtieth Supplemental Indenture..........................   March 1, 1991
Thirty-first Supplemental Indenture.......................   May 1, 1991
Thirty-second Supplemental Indenture......................   July 1, 1991
Thirty-third Supplemental Indenture.......................   February 1, 1992
Thirty-fourth Supplemental Indenture......................   April 1, 1992
Thirty-fifth Supplemental Indenture.......................   April 1, 1992
Thirty-sixth Supplemental Indenture.......................   June 1, 1992
Thirty-seventh Supplemental Indenture.....................   June 1, 1992
Thirty-eighth Supplemental Indenture......................   August 1, 1992
Thirty-ninth Supplemental Indenture.......................   October 1, 1992
Fortieth Supplemental Indenture...........................   November 1, 1992
Forty-first Supplemental Indenture........................   December 1, 1992
Forty-second Supplemental Indenture.......................   March 1, 1993
Forty-third Supplemental Indenture........................   April 1, 1993
Forty-fourth Supplemental Indenture.......................   April 1, 1993
Forty-fifth Supplemental Indenture........................   May 1, 1993
Forty-sixth Supplemental Indenture........................   July 1, 1993
Forty-seventh Supplemental Indenture......................   October 1, 1993
Forty-eighth Supplemental Indenture.......................   November 1, 1993
Forty-ninth Supplemental Indenture........................   May 1, 1994
Fiftieth Supplemental Indenture...........................   May 1, 1994
Fifty-first Supplemental Indenture........................   August 1, 1994
Fifty-second Supplemental Indenture.......................   April 1, 1995
Fifty-third Supplemental Indenture........................   June 1, 1995
Fifty-fourth Supplemental Indenture.......................   October 1, 1995
Fifty-fifth Supplemental Indenture........................   March 1, 1996
Fifty-sixth Supplemental Indenture........................   September 1, 1996
Fifty-seventh Supplemental Indenture......................   February 1, 1997
Fifty-eighth Supplemental Indenture.......................   July 1, 1997

which supplemental indentures were or are to be recorded or filed as required in
the State of Texas; and

     WHEREAS, by the Original Indenture, the Company covenanted that it would
execute and deliver such supplemental indenture or indentures and such further
instruments and do such further acts as may be necessary or proper to carry out
more effectually the purposes of the Mortgage and to make subject to the Lien of
the Mortgage any property thereafter acquired and intended to be subject to the
Lien thereof; and

                                  3
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     WHEREAS, in addition to the property described in the Original Indenture,
the Company has acquired certain other property, rights and interests in
property; and

     WHEREAS, the Company has heretofore issued as of February 28, 1999, in
accordance with the provisions of the Original Indenture, as heretofore
supplemented, the following series of First Mortgage and Collateral Trust Bonds
and First Mortgage Bonds:

<TABLE>

<CAPTION>
                                                             Principal          Principal
                                                              Amount             Amount
                   Series                                      Issued          Outstanding

<S>                                                        <C>                    <C>
12% Series due March 1, 1985...........................    $   1,000,000          $    None
13 5/8% Series due April 1, 2014.......................      100,000,000               None
13 1/2% Series due September 1, 2014...................      150,000,000               None
12 7/8% Series due April 1, 2015.......................      150,000,000               None
12% Series due August 1, 2015..........................      100,000,000               None
12% Series due September 1, 2015.......................       75,000,000               None
11 1/8% Series due December 1, 2015....................      150,000,000               None
9 3/8% Series due March 1, 2016........................      200,000,000               None
9 3/4% Series due May 1, 2016..........................      200,000,000               None
Pollution Control Series C.............................       70,000,000               None
Pollution Control Series D.............................      200,000,000               None
9 1/2% Series due December 1, 2016.....................      300,000,000               None
9 1/4% Series due February 1, 2017.....................      250,000,000               None
Pollution Control Series E.............................      100,000,000               None
10 1/2% Series due April 1, 2017.......................      250,000,000               None
9 1/2% Series due July 1, 1997.........................      150,000,000               None
10 1/2% Series due July 1, 2017........................      150,000,000               None
Pollution Control Series F ............................       55,000,000               None
Pollution Control Series G ............................       12,000,000               None
Pollution Control Series H ............................      112,000,000               None
Pollution Control Series I ............................      100,000,000               None
10 3/8% Series due May 1, 1998.........................      150,000,000               None
11 3/8% Series due May 1, 2018.........................      150,000,000               None
Secured Medium-Term Notes, Series A....................      300,000,000               None
10.44% Series due November 1, 2008.....................      150,000,000          3,000,000
Pollution Control Series J ............................      100,000,000        100,000,000
9 1/2% Series due August 1, 1999.......................      200,000,000        200,000,000
10% Series due August 1, 2019..........................      100,000,000               None
9 7/8% Series due November 1, 2019.....................      150,000,000               None
Secured Medium-Term Notes, Series B....................      150,000,000        114,200,000
Pollution Control Series K ............................       50,000,000         50,000,000
Pollution Control Series L ............................       40,000,000         40,000,000
10 5/8% Series due September 1, 2020...................      250,000,000               None
Secured Medium-Term Notes, Series C....................      150,000,000               None
8 1/4% Pollution Control Series due October 1, 2020....       11,000,000         11,000,000
7 7/8% Pollution Control Series due March 1, 2021......      100,000,000        100,000,000
9 3/4% Series due May 1, 2021..........................      300,000,000        133,047,000
Pollution Control Series M due June 1, 2021 ...........       86,250,000               None
Pollution Control Series N due June 1, 2021 ...........       57,500,000               None
Pollution Control Series O due June 1, 2021 ...........       57,500,000               None

                                  4
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Pollution Control Series P due June 1, 2021 ...........     $115,000,000       $ 18,325,250
8 1/8% Series due February 1, 2002.....................      150,000,000        150,000,000
8 7/8% Series due February 1, 2022.....................      175,000,000        117,200,000
8 1/4% Series due April 1, 2004........................      100,000,000        100,000,000
9% Series due April 1, 2022............................      100,000,000               None
6 3/4% Pollution Control Series due April 1, 2022......       50,000,000         50,000,000
7 1/8% Series due June 1, 1997.........................      150,000,000               None
8% Series due June 1, 2002.............................      147,000,000        147,000,000
6 5/8% Pollution Control Series due June 1, 2022.......       33,000,000         33,000,000
6 3/8% Series due August 1, 1997.......................      175,000,000               None
7 3/8% Series due August 1, 2001.......................      150,000,000        150,000,000
8 1/2% Series due August 1, 2024.......................      175,000,000        127,000,000
6.70% Pollution Control Series due October 1, 2022.....       16,935,000         16,935,000
6.55% Pollution Control Series due October 1, 2022.....       40,000,000         40,000,000
7 3/8% Series due November 1, 1999.....................      100,000,000        100,000,000
8 3/4% Series due November 1, 2023.....................      200,000,000        121,950,000
6 1/2% Pollution Control Series due December 1, 2027...       46,660,000         46,660,000
6 3/4% Series due March 1, 2003........................      200,000,000        200,000,000
7 7/8% Series due March 1, 2023........................      300,000,000        168,100,000
6.05% Pollution Control Series due April 1, 2025.......       90,000,000         90,000,000
6.10% Pollution Control Series due April 1, 2028.......       50,000,000         50,000,000
5 7/8% Series due April 1, 1998........................      175,000,000               None
6 3/4% Series due April 1, 2003........................      100,000,000        100,000,000
7 7/8% Series due April 1, 2024........................      225,000,000        150,183,000
Pollution Control Series due June 1, 2023..............      115,000,000        115,000,000
5 3/4% Series due July 1, 1998.........................      150,000,000               None
6 3/4% Series due July 1, 2005.........................      100,000,000         90,000,000
7 5/8% Series due July 1, 2025.........................      250,000,000        210,000,000
5 1/2% Series due October 1, 1998......................      125,000,000               None
6 1/4% Series due October 1, 2004......................      125,000,000        115,000,000
7 3/8% Series due October 1, 2025......................      300,000,000        193,000,000
5 1/2% Pollution Control Series due May 1, 2022........       50,000,000         50,000,000
5.55% Pollution Control Series due May 1, 2022.........       75,000,000         75,000,000
5.85% Pollution Control Series due May 1, 2022.........       33,465,000         33,465,000
Floating Rate Series due May 1, 1999...................      300,000,000               None
Pollution Control Series Q due May 1, 2029.............       45,045,500         45,045,500
Pollution Control Series R due May 1, 2029.............       45,045,500         45,045,500
0% Series due 1994.....................................    1,013,831,000               None
Pollution Control Series S due April 1, 2030...........       58,270,500         58,270,500
Pollution Control Series T due April 1, 2030...........       18,400,000         18,400,000
Pollution Control Series U.............................      136,108,250        136,108,250
Pollution Control Series V.............................      136,108,250        136,108,250
Pollution Control Series W.............................       13,857,500         13,857,500
Pollution Control Series X.............................       21,246,250         21,246,250
Secured Medium-Term Notes, Series D....................      201,150,000        201,150,000
Pollution Control Series Y.............................       28,819,000         28,819,000
Pollution Control Series Z.............................       66,642,500         66,642,500
Pollution Control Series AA............................       28,750,000         28,750,000
Pollution Control Series AB............................       28,750,000         28,750,000
Pollution Control Series AC............................       70,397,250         70,397,250
Pollution Control Series AD............................       57,500,000         57,500,000

                                  5
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Pollution Control Series AE............................       57,500,000         57,500,000
Pollution Control Series AF............................       36,000,750         36,000,750
Pollution Control Series AG............................       28,801,750         28,801,750
Pollution Control Series AH............................       33,079,750         33,079,250
Pollution Control Series AI  ..........................       59,253,750         59,253,750
Pollution Control Series AJ ...........................       13,800,000         13,800,000

</TABLE>

which bonds are also hereinafter sometimes called bonds of the First through
Ninety-seventh Series, respectively; and

     WHEREAS, Section 2.01 of the Original Indenture provides that the form of
each series of bonds (other than the First Series) issued thereunder and of the
coupons to be attached to coupon bonds of such series shall be established by
Resolution of the Board of Directors of the Company, and that the form of such
series, as established by said Board of Directors, shall specify the descriptive
title of the bonds and various other terms thereof, and may also have such
omissions or modifications or contain such provisions not prohibited by the
provisions of the Mortgage as the Board of Directors may, in its discretion,
cause to be inserted therein expressing or referring to the terms and conditions
upon which such bonds are to be issued and/or secured under the Mortgage; and

     WHEREAS, Section 22.04 of the Original Indenture provides, among other
things, that any power, privilege or right expressly or impliedly reserved to or
in any way conferred upon the Company by any provision of the Mortgage, whether
such power, privilege or right is in any way restricted or is unrestricted, may
be in whole or in part waived or surrendered or subjected to any restriction if
at the time unrestricted, or to additional restriction if already restricted,
and the Company may enter into any further covenants, limitations, restrictions
or provisions for the benefit of any one or more series of bonds issued
thereunder, or the Company may cure any ambiguity contained therein, or in any
supplemental indenture, or may establish the terms and provisions of any series
of bonds other than the First Series, by an instrument in writing executed and
acknowledged by the Company in such manner as would be necessary to entitle a
conveyance of real estate to be recorded in all of the states in which any
property at the time subject to the Lien of the Mortgage shall be situated; and

     WHEREAS, the Company now desires to create a new series of bonds and to add
to its covenants and agreements contained in the Mortgage certain other
covenants and agreements to be observed by it and to alter and amend in certain
respects the covenants and provisions contained in the Mortgage; and

     WHEREAS, the execution and delivery by the Company of this Fifty-ninth
Supplemental Indenture, and the terms of the bonds of the Ninety-eighth Series,
hereinafter referred to, have been duly authorized by the Board of Directors of
the Company by appropriate resolutions of said Board of Directors;


                                  6
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     NOW, THEREFORE, THIS INDENTURE WITNESSETH: That the Company, in
consideration of the premises and of Ten Dollars to it duly paid by the Trustee
at or before the ensealing and delivery of these presents, the receipt whereof
is hereby acknowledged, and in order to secure the payment of both the principal
of and interest and premium, if any, on the bonds from time to time issued under
the Mortgage, according to their tenor and effect and the performance of all the
provisions of the Mortgage (including any instruments supplemental thereto and
any modification made as in the Mortgage provided) and of said bonds, hath
granted, bargained, sold, released, conveyed, assigned, transferred, mortgaged,
hypothecated, affected, pledged, set over and confirmed and granted a security
interest in and by these presents doth grant, bargain, sell, release, convey,
assign, transfer, mortgage, hypothecate, affect, pledge, set over and confirm
and grant a security interest in (subject, however, to Excepted Encumbrances as
defined in Section 1.06 of the Original Indenture) unto The Bank of New York,
Trustee under the Mortgage, and to its successor or successors in said trust,
and to said Trustee and its successors and assigns forever, all properties of
the Company, real, personal and mixed, of the kind or nature specifically
mentioned in the Original Indenture, as heretofore supplemented, or of any other
kind or nature acquired by the Company on or after the date of the execution and
delivery of the Original Indenture (except any herein or in the Original
Indenture expressly excepted), now owned or, subject to the provisions of
Section 18.03 of the Original Indenture, hereafter acquired by the Company (by
purchase, consolidation, merger, donation, construction, erection or in any
other way) and wheresoever situated, including (without in anywise limiting or
impairing by the enumeration of the same, the scope and intent of the foregoing
or of any general description contained in this Fifty-ninth Supplemental
Indenture) all real estate, lands, easements, servitudes, licenses, permits,
franchises, privileges, rights of way and other rights in or relating to real
estate or the occupancy of the same; all power sites, flowage rights, water
rights, water locations, water appropriations, ditches, flumes, reservoirs,
reservoir sites, canals, raceways, waterways, dams, dam sites, aqueducts, and
all other rights or means for appropriating, conveying, storing and supplying
water; all rights of way and roads; all plants for the generation of electricity
by steam, water and/or other power; all power houses, gas plants, street
lighting systems, standards and other equipment incidental thereto; all
telephone, radio and television systems, air-conditioning systems and equipment
incidental thereto, water wheels, water works, water systems, steam heat and hot
water plants, substations, lines, service and supply systems, bridges, culverts,
tracks, ice or refrigeration plants and equipment, offices, buildings and other
structures and the equipment thereof; all machinery, engines, boilers, dynamos,
turbines, electric, gas and other machines, prime movers, regulators, meters,
transformers, generators (including, but not limited to, engine driven
generators and turbo-generator units), motors, electrical, gas and mechanical
appliances, conduits, cables, water, steam heat, gas or other pipes, gas mains
and pipes, service pipes, fittings, valves and connections, pole and
transmission lines, towers, overhead conductors and devices, underground
conduits, underground conductors and devices, wires, cables, tools, implements,
apparatus, storage battery equipment, and all other fixtures and personalty; all
municipal and other franchises, consents or permits; all lines for the
transmission and distribution of electric current, gas, steam heat or water for
any purpose including towers, poles, wires, cables, pipes, conduits, ducts and
all apparatus for use in connection therewith and (except as herein or in the
Original Indenture expressly excepted) all the right, title and interest of the

                                  7
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Company in and to all other property of any kind or nature appertaining to
and/or used and/or occupied and/or enjoyed in connection with any property
hereinbefore or in the Original Indenture described.

     TOGETHER WITH all and singular the tenements, hereditaments, prescriptions,
servitudes and appurtenances belonging or in anywise appertaining to the
aforesaid property or any part thereof, with the reversion and reversions,
remainder and remainders and (subject to the provisions of Section 13.01 of the
Original Indenture) the tolls, rents, revenues, issues, earnings, income,
product and profits thereof, and all the estate, right, title and interest and
claim whatsoever, at law as well as in equity, which the Company now has or may
hereafter acquire in and to the aforesaid property and franchises and every part
and parcel thereof.

     IT IS HEREBY AGREED by the Company that, subject to the provisions of
Section 18.03 of the Original Indenture, all the property, rights and franchises
acquired by the Company (by purchase, consolidation, merger, donation,
construction, erection or in any other way) after the date hereof, except any
herein or in the Original Indenture expressly excepted, shall be and are as
fully granted and conveyed hereby and as fully embraced within the Lien of the
Original Indenture and the Lien hereof as if such property, rights and
franchises were now owned by the Company and were specifically described herein
and conveyed hereby.

     PROVIDED that the following are not and are not intended to be now or
hereafter granted, bargained, sold, released, conveyed, assigned, transferred,
mortgaged, hypothecated, affected, pledged, set over or confirmed hereunder, nor
is a security interest therein hereby or by the Original Indenture, as
heretofore supplemented, granted or intended to be granted, and the same are
hereby expressly excepted from the Lien and operation of the Original Indenture,
as heretofore supplemented, and from the Lien and operation of this Fifty-ninth
Supplemental Indenture, viz.: (1) cash, shares of stock, bonds, notes and other
obligations and other securities not hereinbefore or hereafter specifically
pledged, paid, deposited, delivered or held under the Mortgage or covenanted so
to be; (2) merchandise, equipment, apparatus, materials or supplies held for the
purpose of sale or other disposition in the usual course of business or for the
purpose of repairing or replacing (in whole or in part) any rolling stock,
buses, motor coaches, automobiles or other vehicles or aircraft or boats, ships,
or other vessels and any fuel, oil and similar materials and supplies consumable
in the operation of any of the properties of the Company; rolling stock, buses,
motor coaches, automobiles and other vehicles and all aircraft; boats, ships and
other vessels; all timber, minerals, mineral rights and royalties; (3) bills,
notes and other instruments and accounts receivable, judgments, demands, general
intangibles and choses in action, and all contracts, leases and operating
agreements not specifically pledged hereunder or under the Mortgage or
covenanted so to be; (4) the last day of the term of any lease or leasehold
which may hereafter become subject to the Lien of the Mortgage; (5) electric
energy, gas, water, steam, ice, and other materials or products generated,
manufactured, produced, or purchased by the Company for sale, distribution or
use in the ordinary course of its business; (6) any natural gas wells or natural
gas leases or natural gas transportation lines or other works or property used

                                  8
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primarily and principally in the production of natural gas or its
transportation, primarily for the purpose of sale to natural gas customers or to
a natural gas distribution or pipeline company, up to the point of connection
with any distribution system; and (7) the Company's franchise to be a
corporation; provided, however, that the property and rights expressly
excepted  from the Lien and  operation of the Original  Indenture and
this Fifty-ninth  Supplemental  Indenture in the above  subdivisions (2)
and (3) shall (to the extent  permitted by law) cease to be so excepted in
the event and as of the date that the  Trustee or a receiver  or trustee
shall enter upon and take possession of the Mortgaged and Pledged  Property
in the manner provided in Article XV of the Original Indenture by reason
of the occurrence of a Default.

     TO HAVE AND TO HOLD all such properties, real, personal and mixed, granted,
bargained, sold, released, conveyed, assigned, transferred, mortgaged,
hypothecated, affected, pledged, set over or confirmed or in which a security
interest has been granted by the Company as aforesaid, or intended so to be
(subject, however, to Excepted Encumbrances as defined in Section 1.06 of the
Original Indenture), unto The Bank of New York, Trustee, and its successors and
assigns forever.

     IN TRUST NEVERTHELESS, for the same purposes and upon the same terms,
trusts and conditions and subject to and with the same provisos and covenants as
are set forth in the Original Indenture, as heretofore supplemented, this
Fifty-ninth Supplemental Indenture being supplemental to the Original Indenture.

     AND IT IS HEREBY COVENANTED by the Company that all the terms, conditions,
provisos, covenants and provisions contained in the Original Indenture, as
heretofore supplemented, shall affect and apply to the property hereinbefore
described and conveyed and to the estate, rights, obligations and duties of the
Company and the Trustee and the beneficiaries of the trust with respect to said
property, and to the Trustee and its successors as Trustee of said property, in
the same manner and with the same effect as if said property had been owned by
the Company at the time of the execution of the Original Indenture, and had been
specifically and at length described in and conveyed to said Trustee by the
Original Indenture as a part of the property therein stated to be conveyed.

     The Company further covenants and agrees to and with the Trustee and its
successors in said trust under the Mortgage, as follows:


                                    ARTICLE I

                          Ninety-eighth Series of Bonds

     SECTION 1. There shall be a series of bonds designated "Pollution Control
Series AK" (herein sometimes referred to as the "Ninety-eighth Series"), each of
which shall also bear the descriptive title "First Mortgage Bond", and the form
thereof, which shall be established in accordance with a Resolution of the Board
of Directors of the Company, shall contain suitable provisions with respect to
the matters hereinafter in this Section specified. Bonds of the Ninety-eighth
Series may be issued in one or more tranches and may be issued with up to one

                                  9
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month's accrued interest. Bonds of the Ninety-eighth Series shall be issued as
fully registered bonds in denominations of One Dollar and, at the option of the
Company, in any multiple or multiples thereof (the exercise of such option to be
evidenced by the execution and delivery thereof); Bonds of the Ninety-eighth
Series shall mature on such date not later than the maturity date of the Series
1999A Brazos Revenue Bonds, referred to below, shall bear interest at such rate
or rates, payable on such date or dates, and have such other terms and
provisions not inconsistent with the Original Indenture as the proper officer or
officers of the Company may determine in accordance with one or more Resolutions
filed with the Trustee referring to this Fifty-ninth Supplemental Indenture
(such determinations shall be evidenced by or in accordance with one or more
written orders filed with the Trustee for the authentication and delivery of
bonds of the Ninety-eighth Series and shall constitute determinations of the
Board of Directors with respect to such bonds for purposes of the Mortgage), the
principal of each said bond to be payable at the office or agency of the Company
in the Borough of Manhattan, The City of New York, New York, or at the office or
agency of the Company in the City of Dallas, Texas, as the holder of any said
bond may elect, in such coin or currency of the United States of America as at
the time of payment is legal tender for public and private debts. Bonds of the
Ninety-eighth Series shall be dated as in Section 2.03 of the Original Indenture
provided.

     (I) The bonds of the Ninety-eighth Series shall be initially issued in an
aggregate principal amount not to exceed $123,036,585 to, and registered in the
name of, the trustee under the Trust Indenture, dated as of March 1, 1999
(hereinafter sometimes called the "1999A Brazos Bond Indenture"), of the Brazos
River Authority (hereinafter sometimes called the "Brazos Authority"), under
which its Collateralized Pollution Control Revenue Refunding Bonds (Texas
Utilities Electric Company Project), Series 1999A (hereinafter sometimes called
the "Series 1999A Brazos Revenue Bonds") are to be issued, in order to provide
the benefit of a lien to secure the obligation of the Company to make the
Installment Payments and Purchase Price payments pursuant to, and as such terms
are defined in, the Installment Payment and Bond Amortization Agreement, dated
as of March 1, 1999 (hereinafter sometimes called the "1999A Brazos Agreement"),
between the Brazos Authority and the Company. The maximum amount of bonds of the
Ninety-eighth Series that may be issued is unlimited but the aggregate principal
amount of bonds of the Ninety-eighth Series at any one time Outstanding shall
not exceed $127,126,750. The maximum stated interest rate for any bonds of the
Ninety-eighth Series shall not exceed 15% per annum.

     The Company shall receive a credit against its obligation to make any
payment of the principal of and interest, if any, on any tranche of the bonds of
the Ninety-eighth Series, whether at maturity, upon redemption or otherwise, in
an amount equal to (x) the sum of (a) the amount, if any, on deposit in the Debt
Service Fund maintained under the 1999A Brazos Bond Indenture which reduces the
corresponding Installment Payment and (b) the amount, if any, paid by the
Company pursuant to Section 5.04 of the 1999A Brazos Agreement in respect of the
corresponding Installment Payment multiplied by (y) the ratio of the principal
amount of Outstanding bonds of the Ninety-eighth Series to the principal amount

                                  10
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<PAGE>


of outstanding Series 1999A Brazos Revenue Bonds, in each case immediately prior
thereto.

     The Trustee may conclusively presume that the obligation of the Company to
pay the principal of, and interest, if any, on any tranche of the bonds of the
Ninety-eighth Series as the same shall become due and payable shall have been
fully satisfied and discharged unless and until it shall have received a written
notice from the trustee under the 1999A Brazos Bond Indenture, signed by the
President, a Vice President or a Trust Officer of such trustee, stating that the
corresponding Installment Payment or Purchase Price payment has become due and
payable and has not been fully paid and specifying the amount of funds required
to make such payment.

     (II) In the event that any Series 1999A Brazos Revenue Bonds outstanding
under the 1999A Brazos Bond Indenture shall become immediately due and payable
pursuant to Section 6.02 of the 1999A Brazos Bond Indenture, all bonds of the
Ninety-eighth Series, then Outstanding, shall be redeemed by the Company, on the
date such Series 1999A Brazos Revenue Bonds shall have become immediately due
and payable, at the principal amount thereof.

     The Trustee may conclusively presume that no redemption of bonds of the
Ninety-eighth Series is required pursuant to the first paragraph of this
subsection (II) unless and until it shall have received a written notice from
the trustee under the 1999A Brazos Bond Indenture, signed by the President, a
Vice President or a Trust Officer of such trustee, stating that Series 1999A
Brazos Revenue Bonds have become immediately due and payable pursuant to Section
6.02 of the 1999A Brazos Bond Indenture, and specifying the principal amount
thereof. Said notice shall also contain a waiver of notice of such redemption by
the trustee under the 1999A Brazos Bond Indenture, as the holder of all bonds of
the Ninety-eighth Series then Outstanding.

     (III) The Company hereby waives its right to have any notice of redemption
pursuant to subsection (II) of this Section 1 state that such notice is subject
to the receipt of the redemption moneys by the Trustee on or before the date
fixed for redemption. Notwithstanding the provisions of Section 12.02 of the
Mortgage, any such notice under such subsection shall not be conditional.

     (IV) At the option of the registered owner, any bonds of the Ninety-eighth
Series, upon surrender thereof for cancellation at the office or agency of the
Company in the Borough of Manhattan, The City of New York, New York, shall be
exchangeable for a like aggregate principal amount of bonds of the same series
of other authorized denominations.

     Bonds of the Ninety-eighth Series shall not be transferable except to any
successor trustee under the 1999A Brazos Bond Indenture, any such transfer to be
made at the office or agency of the Company in the Borough of Manhattan, The
City of New York, New York.

                                  11
<PAGE>
<PAGE>


     The Company hereby waives any right to make a charge for any exchange or
transfer of bonds of the Ninety-eighth Series.


                                   ARTICLE II

                            Miscellaneous Provisions

      SECTION 2. Subject to the amendments provided for in this Fifty-ninth
Supplemental  Indenture,  the  terms  defined  in  the  Original  Indenture,  as
heretofore supplemented, shall for all purposes of this Fifty-ninth Supplemental
Indenture have the meanings specified in the Original  Indenture,  as heretofore
supplemented.

     SECTION 3. The Trustee hereby accepts the trusts herein declared, provided,
created or supplemented and agrees to perform the same upon the terms and
conditions herein and in the Original Indenture, as heretofore supplemented, set
forth and upon the following terms and conditions:

     The Trustee shall not be responsible in any manner whatsoever for or in
respect of the validity or sufficiency of this Fifty-ninth Supplemental
Indenture or for or in respect of the recitals contained herein, all of which
recitals are made by the Company solely. In general, each and every term and
condition contained in Article XIX of the Original Indenture shall apply to and
form part of this Fifty-ninth Supplemental Indenture with the same force and
effect as if the same were herein set forth in full with such omissions,
variations and insertions, if any, as may be appropriate to make the same
conform to the provisions of this Fifty-ninth Supplemental Indenture.

     SECTION 4. Whenever in this Fifty-ninth Supplemental Indenture either of
the parties hereto is named or referred to, this shall, subject to the
provisions of Articles XVIII and XIX of the Original Indenture, be deemed to
include the successors and assigns of such party, and all the covenants and
agreements in this Fifty-ninth Supplemental Indenture contained, by or on behalf
of the Company, or by or on behalf of the Trustee, shall, subject as aforesaid,
bind and inure to the respective benefits of the respective successors and
assigns of such parties, whether so expressed or not.

     SECTION 5. Nothing in this Fifty-ninth Supplemental Indenture expressed or
implied, is intended, or shall be construed to confer upon, or to give to, any
person, firm or corporation, other than the parties hereto and the holders of
the bonds and coupons Outstanding under the Mortgage, any right, remedy or claim
under or by reason of this Fifty-ninth Supplemental Indenture or any covenant,
condition, stipulation, promise or agreement hereof, and all the covenants,
conditions, stipulations, promises and agreements in this Fifty-ninth
Supplemental Indenture contained, by or on behalf of the Company, shall be for
the sole and exclusive benefit of the parties hereto, and of the holders of the
bonds and coupons Outstanding under the Mortgage.

                                  12
<PAGE>
<PAGE>


     SECTION 6. This Fifty-ninth Supplemental Indenture shall be executed in
several counterparts, each of which shall be an original and all of which shall
constitute but one and the same instrument.

                                  13
<PAGE>
<PAGE>



     IN WITNESS WHEREOF, TEXAS UTILITIES ELECTRIC COMPANY has caused its
corporate name to be hereunto affixed, and this instrument to be signed and
sealed by its Chairman of the Board and Chief Executive, President or one of its
Vice Presidents, and its corporate seal to be attested by its Secretary or one
of its Assistant Secretaries for and in its behalf, and THE BANK OF NEW YORK has
caused its corporate name to be hereunto affixed, and this instrument to be
signed and sealed by one of its Vice Presidents or Assistant Vice Presidents and
its corporate seal to be attested by one of its Assistant Vice Presidents,
Assistant Secretaries or Assistant Treasurers, all as of the day and year first
above written.

                                              TEXAS UTILITIES ELECTRIC COMPANY


                                              By  /s/ John H. Carlson
                                                -------------------------------
                                                  JOHN H. CARLSON
                                                  Vice President


Attest:

 /s/ John F. Stephens, Jr.
----------------------------------
     JOHN F. STEPHENS, JR.
     Assistant Secretary



Executed, sealed and delivered by
  TEXAS UTILITIES ELECTRIC COMPANY in the presence of:


 /s/ Justin B. Rhodes
----------------------------------


 /s/ Craig Taylor
----------------------------------


                                  14
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<PAGE>



                                              THE BANK OF NEW YORK,
                                                  Trustee


                                              By  /s/ W.N. Gitlin
                                                -----------------------------
                                                  W. N. GITLIN
                                                  Vice President

Attest:

  /s/ Remo J. Reale
----------------------------------
     REMO J. REALE
     Assistant Vice President


Executed, sealed and delivered by
  THE BANK OF NEW YORK
   in the presence of:


 /s/ Mary LaGumina
----------------------------------


 /s/ Thomas B. Zakrzewski
----------------------------------



<PAGE>
                                  15


STATE OF TEXAS ...............)
                              )  SS.:
COUNTY OF DALLAS..............)


     Before me, a Notary Public in and for said State, on this day personally
appeared JOHN H. CARLSON, known to me to be the person whose name is subscribed
to the foregoing instrument and known to me to be a Vice President of TEXAS
UTILITIES ELECTRIC COMPANY, a Texas corporation, and acknowledged to me that
said person executed said instrument for the purposes and consideration therein
expressed, and as the act of said corporation.

     Given under my hand and seal of office this 22nd day of March, 1999.


                          /s/ Julia Laxson
                        ----------------------------------
                                  JULIA LAXSON
                          Notary Public, State of Texas
                    My Commission Expires February 26, 2001


                                  16
<PAGE>
<PAGE>



STATE OF NEW YORK                 )
                                  )  SS.:
COUNTY OF NEW YORK                )


     Before me, a Notary Public in and for said State, on this day personally
appeared W.N. GITLIN, known to me to be the person whose name is subscribed to
the foregoing instrument and known to me to be a Vice President of THE BANK OF
NEW YORK, a New York corporation, and acknowledged to me that said person
executed said instrument for the purposes and consideration therein expressed,
and as the act of said corporation.

     Given under my hand and seal of office this 30th day of March, 1999.



                           /s/ William J. Cassels
                        --------------------------------
                               WILLIAM J. CASSELS
                        Notary Public, State of New York
                                 No. 01CA5027729
                            Qualified in Bronx County
                      Certificate filed in New York County
                         Commission Expires May 16, 2000