<PAGE>

                                                                 EXHIBIT 4(B).19

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


                                   PP&L, INC
                 (formerly Pennsylvania Power & Light Company)

                                      TO

                             BANKERS TRUST COMPANY

           (successor to Morgan Guaranty Trust Company of New York,
                 formerly Guaranty Trust Company of New York)



                         As Trustee under PP&L, Inc.'s
                          Mortgage and Deed of Trust,
                          Dated as of October 1, 1945

                           ________________________

                     Sixty-seventh Supplemental Indenture



                       Providing among other things for
                   First Mortgage Bonds, Short-Term Series B

                           ________________________

                           Dated as of June 1, 1999

-------------------------------------------------------------------------------
<PAGE>

                     SIXTY-SEVENTH SUPPLEMENTAL INDENTURE

     SIXTY-SEVENTH SUPPLEMENTAL INDENTURE, dated as of the 1st day of June, 1999
made and entered into by and between PP&L, INC. (formerly Pennsylvania Power &
Light Company), a corporation of the Commonwealth of Pennsylvania, whose address
is Two North Ninth Street, Allentown, Pennsylvania 18101 (hereinafter sometimes
called the Company), and BANKERS TRUST COMPANY (successor to MORGAN GUARANTY
TRUST COMPANY OF NEW YORK, formerly GUARANTY TRUST COMPANY OF NEW YORK), a
corporation of the State of New York, whose address is 130 Liberty Street, New
York, New York 10006 (hereinafter sometimes called the Trustee), as Trustee
under the Mortgage and Deed of Trust, dated as of October 1, 1945 (hereinafter
called the Mortgage and, together with any indentures supplemental thereto,
hereinafter called the Indenture), which Mortgage was executed and delivered by
Pennsylvania Power & Light 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 said Mortgage is hereby made, this instrument (hereinafter called the
Sixty-seventh Supplemental Indenture) being supplemental thereto;

     WHEREAS, said Mortgage was or is to be recorded in various Counties in the
Commonwealth of Pennsylvania, which Counties include or will include all
Counties in which this Sixty-seventh Supplemental Indenture is to be recorded;
and

     WHEREAS, by an amendment to its Articles of Incorporation filed with the
Office of the Secretary of State of Pennsylvania on September 12, 1997, the
Company changed its name to PP&L, Inc.; and

     WHEREAS, an instrument, dated August 5, 1994, was executed by the Company
appointing Bankers Trust Company as Trustee in succession to said Morgan
Guaranty Trust Company of New York (resigned) under the Indenture, and by
Bankers Trust Company accepting said appointment, which instrument was or is to
be recorded in various Counties in the Commonwealth of Pennsylvania; and

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

     WHEREAS, the Company executed and delivered as supplements to the Mortgage,
the following supplemental indentures:

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

     First Supplemental Indenture..................    July 1, 1947
     Second Supplemental Indenture.................    December 1, 1948
     Third Supplemental Indenture..................    February 1, 1950
     Fourth Supplemental Indenture.................    March 1, 1953
     Fifth Supplemental Indenture..................    August 1, 1955
     Sixth Supplemental Indenture..................    December 1, 1961
     Seventh Supplemental Indenture................    March 1, 1964
     Eighth Supplemental Indenture.................    June 1, 1966
     Ninth Supplemental Indenture..................    November 1, 1967
     Tenth Supplemental Indenture..................    December 1, 1967
     Eleventh Supplemental Indenture...............    January 1, 1969
     Twelfth Supplemental Indenture................    June 1, 1969
     Thirteenth Supplemental Indenture.............    March 1, 1970
     Fourteenth Supplemental Indenture.............    February 1, 1971
     Fifteenth Supplemental Indenture..............    February 1, 1972
     Sixteenth Supplemental Indenture..............    January 1, 1973
<PAGE>

                                      -2-

     Designation                                       Dated as of
     -----------                                       -----------
     Seventeenth Supplemental Indenture............    May 1, 1973
     Eighteenth Supplemental Indenture.............    April 1, 1974
     Nineteenth Supplemental Indenture.............    October 1, 1974
     Twentieth Supplemental Indenture..............    May 1, 1975
     Twenty-first Supplemental Indenture...........    November 1, 1975
     Twenty-second Supplemental Indenture..........    December 1, 1976
     Twenty-third Supplemental Indenture...........    December 1, 1977
     Twenty-fourth Supplemental Indenture..........    April 1, 1979
     Twenty-fifth Supplemental Indenture...........    April 1, 1980
     Twenty-sixth Supplemental Indenture...........    June 1, 1980
     Twenty-seventh Supplemental Indenture.........    June 1, 1980
     Twenty-eighth Supplemental Indenture..........    December 1, 1980
     Twenty-ninth Supplemental Indenture...........    February 1, 1981
     Thirtieth Supplemental Indenture..............    February 1, 1981
     Thirty-first Supplemental Indenture...........    September 1, 1981
     Thirty-second Supplemental Indenture..........    April 1, 1982
     Thirty-third Supplemental Indenture...........    August 1, 1982
     Thirty-fourth Supplemental Indenture..........    October 1, 1982
     Thirty-fifth Supplemental Indenture...........    November 1, 1982
     Thirty-sixth Supplemental Indenture...........    February 1, 1983
     Thirty-seventh Supplemental Indenture.........    November 1, 1983
     Thirty-eighth Supplemental Indenture..........    March 1, 1984
     Thirty-ninth Supplemental Indenture...........    April 1, 1984
     Fortieth Supplemental Indenture...............    August 15, 1984
     Forty-first Supplemental Indenture............    December 1, 1984
     Forty-second Supplemental Indenture...........    June 15, 1985
     Forty-third Supplemental Indenture............    October 1, 1985
     Forty-fourth Supplemental Indenture...........    January 1, 1986
     Forty-fifth Supplemental Indenture............    February 1, 1986
     Forty-sixth Supplemental Indenture............    April 1, 1986
     Forty-seventh Supplemental Indenture..........    October 1, 1986
     Forty-eighth Supplemental Indenture...........    March 1, 1988
     Forty-ninth Supplemental Indenture............    June 1, 1988
     Fiftieth Supplemental Indenture...............    January 1, 1989
     Fifty-first Supplemental Indenture............    October 1, 1989
     Fifty-second Supplemental Indenture...........    July 1, 1991
     Fifty-third Supplemental Indenture............    May 1, 1992
     Fifty-fourth Supplemental Indenture...........    November 1, 1992
     Fifty-fifth Supplemental Indenture............    February 1, 1993
     Fifty-sixth Supplemental Indenture............    April 1, 1993
     Fifty-seventh Supplemental Indenture..........    June 1, 1993
     Fifty-eighth Supplemental Indenture...........    October 1, 1993
     Fifty-ninth Supplemental Indenture............    February 15, 1994
     Sixtieth Supplemental Indenture...............    March 1, 1994
     Sixty-first Supplemental Indenture............    March 15, 1994
     Sixty-second Supplemental Indenture...........    September 1, 1994
     Sixty-third Supplemental Indenture............    October 1, 1994
     Sixty-fourth Supplemental Indenture...........    August 1, 1995
<PAGE>

                                      -3-

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

     Sixty-fifth Supplemental Indenture............    April 1, 1997
     Sixty-sixth Supplemental Indenture............    May 1, 1998

which supplemental indentures were or are to be recorded in various Counties in
the Commonwealth of Pennsylvania; and

     WHEREAS, the Company executed and delivered its Supplemental Indenture,
dated July 1, 1954, creating a security interest in certain personal property of
the Company, pursuant to the provisions of the Pennsylvania Uniform Commercial
Code, as a supplement to the Mortgage, which Supplemental Indenture was filed in
the Office of the Secretary of the Commonwealth of Pennsylvania on July 1, 1954,
and all subsequent supplemental indentures were so filed; and

     WHEREAS, in addition to the property described in the Mortgage, as
heretofore supplemented, the Company has acquired certain other property, rights
and interests in property; and

     WHEREAS, the Company has heretofore issued, in accordance with the
provisions of the Mortgage, as supplemented, the following series of First
Mortgage Bonds:

                                                Principal          Principal
                                                 Amount             Amount
Series                                           Issued           Outstanding
------                                           ------           -----------

3% Series due 1975.....................       $ 93,000,000           None
2-3/4% Series due 1977.................         20,000,000           None
3-1/4% Series due 1978.................         10,000,000           None
2-3/4% Series due 1980.................         37,000,000           None
3-1/2% Series due 1983.................         25,000,000           None
3-3/8% Series due 1985.................         25,000,000           None
4-5/8% Series due 1991.................         30,000,000           None
4-5/8% Series due 1994.................         30,000,000           None
5-5/8% Series due 1996.................         30,000,000           None
6-3/4% Series due 1997.................         30,000,000           None
6-1/2% Series due 1972.................         15,000,000           None
7% Series due 1999.....................         40,000,000           None
8-1/8% Series due June 1, 1999.........         40,000,000           None
9% Series due 2000.....................         50,000,000           None
7-1/4% Series due 2001.................         60,000,000           None
7-5/8% Series due 2002.................         75,000,000           None
7-1/2% Series due 2003.................         80,000,000           None
Pollution Control Series A.............         28,000,000           None
9-1/4% Series due 2004.................         80,000,000           None
10-1/8% Series due 1982................        100,000,000           None
9-3/4% Series due 2005.................        125,000,000           None
9-3/4% Series due November 1, 2005.....        100,000,000           None
8-1/4% Series due 2006.................        150,000,000           None
8-1/2% Series due 2007.................        100,000,000           None
9-7/8% Series due 1983-1985............        100,000,000           None
<PAGE>

                                      -4-

                                                Principal          Principal
                                                 Amount             Amount
Series                                           Issued           Outstanding
------                                           ------           -----------

15-5/8% Series due 2010.................        $100,000,000          None
11-3/4% Series due 1984.................          30,000,000          None
Pollution Control Series B..............          70,000,000          None
Pollution Control Series C..............          20,000,000          None
14% Series due December 1, 1990.........         125,000,000          None
15% Series due 1984-1986................          50,000,000          None
14-3/4% Series A due 1986...............          30,000,000          None
14-3/4% Series B due 1986...............          20,000,000          None
16-1/2% Series due 1987-1991............          52,000,000          None
16-1/8% Series due 1992.................         100,000,000          None
16-1/2% Series due 1986-1990............          92,500,000          None
13-1/4% Series due 2012.................         100,000,000          None
Pollution Control Series D..............          70,000,000          None
12-1/8% Series due 1989-1993............          50,000,000          None
13-1/8% Series due 2013.................         125,000,000          None
Pollution Control Series E..............          37,750,000          None
13-1/2% Series due 1994.................         125,000,000          None
Pollution Control Series F..............         115,500,000          None
12-3/4% Series due 2014.................         125,000,000          None
Pollution Control Series G..............          55,000,000          None
12% Series due 2015.....................         125,000,000          None
10-7/8% Series due 2016.................         125,000,000          None
9-5/8% Series due 1996..................         125,000,000          None
9% Series due 2016......................         125,000,000          None
9-1/2% Series due 2016..................         125,000,000          None
9-1/4% Series due 1998..................         125,000,000          None
9-5/8% Series due 1998..................         125,000,000          None
10% Series due 2019.....................         125,000,000          None
9-1/4% Series due 2019..................         250,000,000      $215,000,000
9-3/8% Series due 2021..................         150,000,000        99,750,000
7-3/4% Series due 2002..................         150,000,000       150,000,000
8-1/2% Series due 2022..................         150,000,000       150,000,000
Pollution Control Series H..............          90,000,000        90,000,000
6-7/8% Series due 2003..................         100,000,000       100,000,000
7-7/8% Series due 2023..................         200,000,000       200,000,000
5-1/2% Series due 1998..................         150,000,000          None
6-1/2% Series due 2005..................         125,000,000       125,000,000
6% Series due 2000......................         125,000,000       125,000,000
6-3/4% Series due 2023..................         150,000,000       150,000,000
Pollution Control Series I..............          53,250,000        53,250,000
6.55% Series due 2006...................         150,000,000       150,000,000
7.30% Series due 2024...................         150,000,000       150,000,000
6-7/8% Series due 2004..................         150,000,000       150,000,000
7-3/8% Series due 2014..................         100,000,000       100,000,000
Pollution Control Series J..............         115,500,000       115,500,000
<PAGE>

                                      -5-

                                                Principal          Principal
                                                 Amount             Amount
Series                                           Issued           Outstanding
------                                           ------           -----------

7.70% Series due 2009.......................    $200,000,000      $200,000,000
Pollution Control Series K..................      55,000,000        55,000,000
Short-Term Series A.........................     800,000,000          None
6 1/8% REset Put Securities Series due 2006.     200,000,000       200,000,000

which bonds are also sometimes called bonds of the First through Seventy-fourth
Series, respectively; and

     WHEREAS, Section 8 of the Mortgage provides that the form of each series of
bonds (other than the First Series) issued thereunder 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 contain such
provisions not inconsistent with the provisions of the Indenture 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 Indenture; and

     WHEREAS, Section 120 of the Mortgage 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 Indenture, 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 future covenants, limitations or restrictions 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 said 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
record in all of the States in which any property at the time subject to the
lien of the Indenture 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, as heretofore
supplemented, 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 Sixty-seventh
Supplemental Indenture, and the terms of the bonds of the Seventy-fifth Series,
hereinafter referred to, have been duly authorized by the Board of Directors of
the Company by appropriate Resolutions of said Board of Directors;

     NOW, THEREFORE, THIS INDENTURE WITNESSETH: That PP&L, Inc., in
consideration of the premises and of One Dollar 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 further evidence of assurance of the estate,
title and rights of the Trustee and in order further to secure the payment both
of the principal of and interest and premium, if any, on the bonds from time to
time issued under the Indenture, according to their tenor and effect and the
performance of all the provisions of the Indenture (including any modification
made as in the Mortgage provided) and of said bonds, hereby grants, bargains,
sells, releases, conveys, assigns, transfers, mortgages, pledges, sets over and
confirms (subject, however, to Excepted Encumbrances as defined in Section 6 of
the Mortgage) unto Bankers Trust Company, as Trustee under the Indenture, and to
its successor or successors in said trust, and to said Trustee and its
successors and assigns forever, all property, real, personal and mixed, of the
kind or nature specifically mentioned in the Mortgage, as heretofore
supplemented, or of any other kind or nature, acquired by the Company after the
date of the execution and delivery of the Sixty-sixth Supplemental Indenture
(except any herein or in the Mortgage, as heretofore supplemented, expressly
excepted and except any which may not lawfully be mortgaged or pledged under the
Indenture), now owned
<PAGE>

                                      -6-

or, subject to the provisions of Section 87 of the Mortgage, 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) all lands, power sites, flowage rights, water rights,
water locations, water appropriations, ditches, flumes, reservoirs, reservoir
sites, canals, raceways, 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, telephone, radio and
television systems, air-conditioning systems and equipment incidental thereto,
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, electric, gas and other
machines, regulators, meters, transformers, generators, 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, wires, cables, tools, implements, apparatus,
furniture and chattels; 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; 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 and (except as herein or in the Mortgage, as heretofore supplemented,
expressly excepted) all the right, title and interest of the 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
Mortgage, as heretofore supplemented, 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 57 of the
Mortgage) 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 87 of the Mortgage and to the extent permitted by law, 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 Mortgage, as heretofore supplemented,
expressly excepted, shall be and are as fully granted and conveyed hereby and as
fully embraced within the lien hereof and the lien of the Indenture, as if such
property, rights and franchises were now owned by the Company and were
specifically described herein and conveyed hereby.

     IT IS HEREBY DECLARED by the Company that all the property, rights and
franchises now owned or hereafter acquired by the Company have been, or are, or
will be owned or acquired with the intention to use the same in carrying on the
business or branches of business of the Company, and it is hereby declared that
it is the intention of the Company that all thereof, except any herein or in the
Mortgage, as heretofore supplemented, expressly excepted, shall (subject to the
provisions of Section 87 of the Mortgage and to the extent permitted by law) be
embraced within the lien of this Sixty-seventh Supplemental Indenture and the
lien of the Indenture.

     PROVIDED that the following are not and are not intended to be now or
hereafter granted, bargained, sold, released, conveyed, assigned, transferred,
mortgaged, pledged, set over or confirmed hereunder and are hereby expressly
excepted from the lien and operation of this Sixty-seventh Supplemental
Indenture and from the lien and operation of the Indenture, viz:  (1) cash,
                                                            ---
shares of stock, bonds, notes and other obligations and other securities not
hereafter specifically pledged, paid, deposited, delivered or held under the
Indenture or covenanted so to be; (2) goods, wares, merchandise, equipment,
apparatus, materials, or supplies held for the purpose of sale or other
disposition in the usual course of business; fuel, oil and similar materials and
supplies consumable in the operation of any of the properties of the Company;
construction equipment acquired for temporary use; all aircraft, rolling stock,
trolley coaches, buses,
<PAGE>

                                      -7-

motor coaches, automobiles and other vehicles and materials and supplies held
for the purposes of repairing or replacing (in whole or part) any of the same;
all timber, minerals, mineral rights and royalties; (3) bills, notes and
accounts receivable, judgments, demands and choses in action, and all contracts,
leases and operating agreements not specifically pledged under the Indenture or
covenanted so to be; the Company's contractual rights or other interest in or
with respect to tires not owned by the Company; (4) the last day of the term of
any lease or leasehold which may be or become subject to the lien of the
Indenture; and (5) electric energy, gas, 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; provided, however,
that the property and rights expressly excepted from the lien and operation of
the 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 XIII of the
Mortgage by reason of the occurrence of a Default as defined in Section 65
thereof, as supplemented by the provisions of this Sixty-seventh Supplemental
Indenture.

     TO HAVE AND TO HOLD all such properties, real, personal and mixed, granted,
bargained, sold, released, conveyed, assigned, transferred, mortgaged, pledged,
set over or confirmed by the Company as aforesaid, or intended so to be, unto
Bankers Trust Company, as 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 Mortgage, as heretofore supplemented, this Sixty-seventh
Supplemental Indenture being supplemental to the Mortgage.

     AND IT IS HEREBY COVENANTED by the Company that all the terms, conditions,
provisos, covenants and provisions contained in the Mortgage, 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 the said property had been owned by the
Company at the time of the execution of the Mortgage, and had been specifically
and at length described in and conveyed to the Trustee by the Mortgage 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 Indenture, as follows:

                                  ARTICLE I.

                         Seventy-fifth Series of Bonds

     SECTION 1.  There shall be a series of bonds designated "Short-Term Series
B" (herein sometimes referred to as the "Seventy-fifth Series"), each of which
shall also bear the descriptive title First Mortgage Bonds, and the form
thereof, which shall be established by 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 Seventy-fifth Series shall
be limited to $600 million in aggregate principal amount (with no more than $200
million in aggregate principal amount to be Outstanding at any one time), except
as provided in Section 16 of the Mortgage, and shall be issued as fully
registered bonds in denominations of One Thousand Dollars and in any multiple or
multiples of One Thousand Dollars; each bond of the Seventy-fifth Series shall
mature on a date not more than sixty days from the date of issue, shall bear
interest at such rate or rates and have such other terms and provisions not
inconsistent with the Mortgage as the Board of Directors may determine in
accordance with one or more resolutions filed with the Trustee and one or more
written orders referring to this Sixty-seventh Supplemental Indenture; the
principal of and interest on each said bond to be payable at the office or
agency of the Company in the Borough of Manhattan, The City of New York, and
interest
<PAGE>

                                      -8-


on each said bond to be also payable at the office of the Company in the City of
Allentown, Pennsylvania, 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 Seventy-fifth Series shall be dated as in Section 10 of the
Mortgage provided.

     Notwithstanding the foregoing, so long as there is no existing default in
the payment of interest on the bonds of the Seventy-fifth Series, the person in
whose name any bond of the Seventy-fifth Series is registered at the close of
business on any Record Date with respect to any interest payment date shall be
entitled to receive the interest payable on such interest payment date; provided
that, interest payable on the maturity date will be payable to the person to
whom the principal thereof shall be payable. "Record Date" for bonds of the
Seventy-fifth Series, shall mean the business day next preceding the
corresponding interest payment date. "Original Interest Accrual Date" with
respect to bonds of the Seventy-fifth Series of a designated interest rate and
maturity shall mean the date of first authentication of Bonds of a designated
interest rate and maturity unless the written order filed for such bonds with
the Trustee on or before such date shall specify another date from which
interest shall accrue, in which case "Original Interest Accrual Date" shall mean
such other date specified in the written order for Bonds of such designated
interest rate and maturity.

     (I)  Each holder of a bond of the Seventy-fifth Series, except as may be
provided in the written order requesting authentication and delivery of such
bond, consents that the bonds of the Seventy-fifth Series may be redeemable at
the option of the Company or pursuant to the requirements of the Indenture in
whole at any time, or in part from time to time, prior to maturity, without
notice provided in Section 52 of the Mortgage, at the principal amount of the
bonds to be redeemed, in each case, together with accrued interest to the date
fixed for redemption by the Company in a notice delivered on or before the date
fixed for redemption by the Company to the Trustee and to the holders of the
bonds to be redeemed.

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

     Bonds of the Seventy-fifth Series shall be transferable, upon the surrender
thereof for cancellation, together with a written instrument of transfer in form
approved by the registrar duly executed by the registered owner or by his duly
authorized attorney, at the office or agency of the Company in the Borough of
Manhattan, The City of New York; provided that such transfer shall not result in
any security being required to be registered under the Securities Act of 1933,
as amended, and an opinion of counsel satisfactory to the Company to such effect
shall have been provided to the Company.

     Upon any transfer or exchange of bonds of the Seventy-fifth Series, the
Company may make a charge therefor sufficient to reimburse it for any tax or
taxes or other governmental charge, as provided in Section 12 of the Mortgage,
but the Company hereby waives any right to make a charge in addition thereto for
any exchange or transfer of bonds of the Seventy-fifth Series.

                                  ARTICLE II.

       Maintenance and Replacement Fund Covenant -- Dividend Covenant --
                   Other Related Provisions of the Mortgage

     SECTION 2.   Subject to the provisions of Section 3 hereof, the Company
covenants and agrees that the provisions of Section 39 of the Mortgage, which
were to remain in effect so long as any bonds of the First Series remained
Outstanding, shall remain in full force and effect so long as any bonds of the
Seventy-fifth Series are Outstanding.
<PAGE>

                                      -9-

     Clause (d) of subsection (II)(B) of Section 4 of the Mortgage, as
heretofore amended, is hereby further amended by inserting the words "and
Seventy-fifth Series" after the words "and Seventy-fourth Series" each time such
words appear therein.

     Clause (6) and clause (e) of Section 5 of the Mortgage and Section 29 of
the Mortgage, as heretofore amended, are hereby further amended by inserting
therein "Seventy-fifth, before "Seventy-fourth," each time such words occur
therein.

                                 ARTICLE III.

                           Miscellaneous Provisions

     SECTION 3.   The Company reserves the right to make such amendments to the
Mortgage, as supplemented, as shall be necessary in order to delete subsection
(I) of Section 39 of the Mortgage, and each holder of bonds of the Seventy-fifth
Series hereby consents to such deletion without any other or further action by
any holder of bonds of the Seventy-fifth Series.

     SECTION 4.   The terms defined in the Mortgage, as heretofore supplemented,
shall, for all purposes of this Sixty-seventh Supplemental Indenture, have the
meanings specified in the Mortgage, as heretofore supplemented.

     SECTION 5.   Whenever in this Sixty-seventh Supplemental Indenture either
of the parties hereto is named or referred to, this shall, subject to the
provisions of Articles XVI and XVII of the Mortgage, be deemed to include the
successors and assigns of such party, and all the covenants and agreements in
this Sixty-seventh 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 6.   So long as any bonds of the Seventy-fifth Series remain
Outstanding, unless this provision shall have been waived in writing by the
holders of seventy per centum (70%) in aggregate principal amount of bonds of
the Seventy-fifth Series Outstanding at the time of such consent, subdivision
(c) of Section 65 of the Mortgage shall read as follows:

                  "(c)  Failure to pay interest or premium, if any, upon or
          principal (whether at maturity as therein expressed or by declaration,
          or otherwise) of any Outstanding Qualified Lien Bonds or of any
          outstanding indebtedness secured by any mortgage or other lien (not
          included in the term Excepted Encumbrances) prior to the lien of this
          Indenture, existing upon any property of the Company which is subject
          to the lien and operation of this Indenture continued beyond the
          period of grace, if any, specified in such mortgage or Qualified Lien
          or other lien securing the same;"

     SECTION 7.   A breach of a specified covenant or agreement of the Company
contained in this Sixty-seventh Supplemental Indenture shall become a Default
under the Indenture upon the happening of the events provided in Section 65(g)
of the Mortgage with respect to such a covenant or agreement.

     SECTION 8.   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 Mortgage, 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 Sixty-seventh Supplemental
Indenture or for or in respect of the recitals contained herein, all of which
<PAGE>

                                      -10-

recitals are made by the Company solely.  Each and every term and condition
contained in Article XVII of the Mortgage, as heretofore amended by said First
through Sixty-sixth Supplemental Indentures, shall apply to and form part of
this Sixty-seventh 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 Sixty-seventh Supplemental Indenture.

     SECTION 9.   Nothing in this Sixty-seventh 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 Indenture, any right,
remedy or claim under or by reason of this Sixty-seventh Supplemental Indenture
or by any covenant, condition, stipulation, promise or agreement hereof, and all
the covenants, conditions, stipulations, promises and agreements in this Sixty-
seventh 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 Indenture.

     SECTION 10.  This Sixty-seventh 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.

     PP&L, INC. does hereby constitute and appoint JAMES E. ABEL, Vice
President -Finance and Treasurer of PP&L, INC., to be its attorney for it, and
in its name and as and for its corporate act and deed to acknowledge this Sixty-
seventh Supplemental Indenture before any person having authority by the laws of
the Commonwealth of Pennsylvania to take such acknowledgment, to the intent that
the same may be duly recorded, and BANKERS TRUST COMPANY does hereby constitute
and appoint JACKIE BARTNICK, a Vice President of BANKERS TRUST COMPANY, to be
its attorney for it, and in its name and as and for its corporate act and deed
to acknowledge this Sixty-seventh Supplemental Indenture before any person
having authority by the laws of the Commonwealth of Pennsylvania to take such
acknowledgment, to the intent that the same may be duly recorded.
<PAGE>

                                      -11-

          IN WITNESS WHEREOF, PP&L, INC. has caused its corporate name to be
hereunto affixed, and this instrument to be signed and sealed by its 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, in the City
of Allentown, Pennsylvania, and BANKERS TRUST COMPANY has caused its corporate
name to be hereunto affixed, and this instrument to be signed and sealed by one
of its Principals, Vice Presidents or Trust Officers, and its corporate seal to
be attested by one of its Vice Presidents, Assistant Vice Presidents or Trust
Officers, in The City of New York, as of the day and year first above written.

                                        PP&L, INC.

                                        By /s/ James E. Abel
                                        --------------------------------------
                                        Vice President - Finance and Treasurer

Attest:

/s/ Diane M. Koch
---------------------------
Assistant Secretary
<PAGE>

                                      -12-

                                   BANKERS TRUST COMPANY, as Trustee

                                   By /s/ Jackie Bartnick
                                   ---------------------------------
                                   Vice President

Attest:

/s/ Vincent Chorney
-----------------------------
Assistant Vice President
<PAGE>

                                      -13-

COMMONWEALTH OF PENNSYLVANIA  )
                              ) ss.:
COUNTY OF LEHIGH              )

     On this ____ day of June, 1999, before me, a notary public, the undersigned
officer, personally appeared  JAMES E. ABEL, who acknowledged himself to be the
Vice President - Finance and Treasurer of PP&L, INC., a corporation and that he,
as such Vice President - Finance and Treasurer, being authorized to do so,
executed the foregoing instrument for the purposes therein contained, by signing
the name of the corporation by himself as Vice President - Finance and
Treasurer.

          In witness whereof, I hereunto set my hand and official seal.

                                   /s/ Francine A. Greenzweig
                                   -------------------------------
                                   Notary Public
<PAGE>

                                      -14-

STATE OF NEW YORK  )
                   ) ss.:
COUNTY OF KINGS    )

     On this 23rd day of June, 1999, before me, a notary public, the undersigned
officer, personally appeared JACKIE BARTNICK, who acknowledged herself to be a
Vice President of BANKERS TRUST COMPANY, a corporation and that she, as such
Vice President, being authorized to do so, executed the foregoing instrument for
the purposes therein contained, by signing the name of the corporation by
herself as Vice President.

          In witness whereof, I hereunto set my hand and official seal.

                                             By: /s/ Boris Treyger
                                                 ------------------------
                                                BORIS TREYGER
                                                Notary Public, State of New York
                                                No. 01TR6016003
                                                Qualified in Kings County
                                                Commission Expires Nov. 9, 2000

     Bankers Trust Company hereby certifies that its precise name and address as
Trustee hereunder are:

                             Bankers Trust Company

                              130 Liberty Street
                           New York, New York 10006

                                   BANKERS TRUST COMPANY

                                   By: /s/ Vincent Chorney
                                       -------------------------
                                       Assistant Vice President