Exhibit 4.1








                               KEYSPAN CORPORATION

                                       AND

                              JPMORGAN CHASE BANK,

                                   as Trustee





                             _______________________

                          FIRST SUPPLEMENTAL INDENTURE

                             Dated as of May 6, 2002

                            ________________________







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     THIS FIRST SUPPLEMENTAL INDENTURE, dated as of May 6, 2002, is between
KEYSPAN CORPORATION, doing business as KeySpan Energy, a corporation duly
incorporated and existing under the laws of the State of New York and having
its principal executive office at One MetroTech Center, Brooklyn, New York
11201 (the "Company"), and JPMORGAN CHASE BANK (formerly, The Chase Manhattan
Bank), a corporation organized and existing under the laws of the State of New
York, acting as Trustee under the Indenture referred to below (the "Trustee").

                              W I T N E S S E T H

     WHEREAS, the Company has duly authorized the execution and delivery of an
Indenture dated as of November 1, 2000 (the "Indenture"), as amended and
supplemented, to provide for the issuance from time to time of its unsecured
notes or other evidences of indebtedness to be issued in one or more series
(the "Securities"), as provided in the Indenture, up to such principal amount
or amounts as may from time to time be authorized in or pursuant to one or
more resolutions of the Board of Directors;

     WHEREAS, pursuant to Section 901 of the Indenture, the Company wishes to
supplement the provisions of the Indenture to provide, among other things, for
the issuance of convertible and exchangeable Securities;

     WHEREAS, the Company has duly authorized the execution and delivery of
this First Supplemental Indenture in order to provide for such modifications
to the Indenture; and

     WHEREAS, all acts and things necessary to make this First Supplemental
Indenture a valid agreement of the Company according to its terms have been
done and performed, and the execution and delivery of this First Supplemental
Indenture have in all respects been duly authorized;

     NOW, THEREFORE, in consideration of the premises and of the purchase and
acceptance of the Securities by the Holders thereof, it is mutually covenanted
and agreed, for the equal and proportionate benefit of the Holders of the
Securities or series thereof, as follows:

     SECTION 1. AMENDMENTS TO THE INDENTURE

     1.1 Amendment to Section 301 of the Indenture. Section 301 is amended by
adding the following clause in numerical order and renumbering the existing
clauses (24) and (25) as clauses (25) and (26), respectively:

     "(24) whether the Securities of the series will be convertible or
exchangeable into other securities of the Company or another Person, and if
so, the terms and conditions upon which such Securities will be so convertible
or exchangeable, including the conversion price or exchange rate and the
conversion or exchange period, and any additions or changes to the Indenture
with respect to the Securities of such series to permit or facilitate such
conversion or exchange (which additions or changes shall not, in any event,
affect the rights, duties or obligations of the Trustee);"


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     1.2 Amendment to Section 401 of the Indenture. Section 401 is amended and
restated as follows:

     "The Company may, at the option of its Board of Directors evidenced by a
Board Resolution set forth in an Officers' Certificate, at any time, with
respect to the Securities of any series, unless otherwise specified pursuant
to Section 301 with respect to a particular series of Securities, elect to
have either Section 402 or 403 be applied to all of the Outstanding Securities
of that series upon compliance with the conditions set forth below in this
Article Four."

     1.3 Amendment to Section 403 of the Indenture. Section 403 is amended by
replacing the phrase "704, 801 and 1007" with the phrase "704, 801, 1007 and
1008 or any covenants established pursuant to Sections 301(26), 901(2) or
901(11)".

     1.4 Amendment to Section 607 of the Indenture. Section 607 of the
Indenture is amended by adding the following paragraphs at the end thereof:

          "When the Trustee incurs expenses or renders services in connection
     with an Event of Default specified in Section 501(5) or (6), the expenses
     (including the reasonable charges and expenses of the Trustee's counsel)
     and the compensation for the services are intended to constitute expenses
     of administration under any bankruptcy law.

          The Company's obligations under this Section 607 and any lien
     arising hereunder shall survive the resignation or removal of the
     Trustee, the discharge of the Company's obligations pursuant to Article
     Four of this Indenture and/or the termination of this Indenture."

     1.5 Amendment to Section 609 of the Indenture. Section 609 is amended by
(i) replacing the heading "Corporate Trustee Required; Different Trustees for
Different Series; Eligibility." with the heading "Corporate Trustee Required;
Eligibility; Different Trustees for Different Series." and (ii) adding the
following paragraph at the end of Section 609:

     "A different Trustee may be appointed by the Company for each series of
Securities prior to the issuance of such Securities. If the initial Trustee
for any series of Securities is to be other than JPMorgan Chase Bank, the
Company and such Trustee shall, prior to the issuance of such Securities,
execute and deliver an indenture supplemental hereto, which shall provide for
the appointment of such Trustee as Trustee for the Securities of such series
and shall add to or change any of the provisions of this Indenture as shall be
necessary to facilitate the administration of the trusts hereunder by more
than one Trustee (which additions or changes shall not, in any event, change
the rights, duties or obligations of JPMorgan Chase Bank or any successor
Trustee), it being understood that nothing herein or in such supplemental
indenture shall constitute such Trustees co-trustees of the same trust and
that each such Trustee shall be trustee of a trust or trusts hereunder
separate and apart from any trust or trusts hereunder administered by any
other such Trustee."

     1.6 Amendment to Section 902 of the Indenture. Section 902 is amended (i)
to add the following at the end of clause (1) thereof:

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     "adversely affect the right to convert or exchange any Security into
other securities of the Company or another Person as may be provided pursuant
to Section 301; or";

and (ii) by replacing each occurrence of the term "1010" in clause (3) thereof
with the term "1009".

     1.7 Amendment to Section 1009 of the Indenture. Section 1009 of the
Indenture is amended by replacing the phrase "1004 to 1009, inclusive," with
the phrase "1004 to 1008, inclusive, or any covenant or condition established
pursuant to Sections 301(26), 901(2) or 901(11)."

     1.8 Addition of Article 14 to the Indenture. The Indenture is amended to
add the following Article 14:

                                  ARTICLE 14.

                            Conversion And Exchange

Section 1401.  Applicability of Article.

     Securities of any series which are designated as being convertible into
or exchangeable for any other security of the Company or another Person prior
to their Stated Maturity shall be convertible or exchangeable in accordance
with their terms and (except as otherwise specified pursuant to Section 301
for the Securities of such series) in accordance with this Article.

Section 1402.  Conversion Privilege.

     A Holder of a Security of a series, which, by its terms, is convertible
into or exchangeable for any other security of the Company or another Person,
may convert or exchange such Security, as the case may be, at any time during
the period and in the manner set forth in the terms of the Securities of such
series. The number of shares or units of such other security issuable upon
conversion of or exchange of a Security shall be determined in the manner set
forth in the terms of such Security.

Section 1403.  Conversion and Exchange Procedure.

     To convert or exchange a Security, as the case may be, the Holder thereof
must comply with and satisfy all of the terms, conditions and other
requirements set forth in the terms of such Security. As soon as practicable,
the Company shall deliver through the relevant conversion or exchange agent a
certificate for the number of shares or units of the security issuable upon
the conversion or exchange.


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Section 1404. Fractional Shares.

     The terms of a convertible or exchangeable Security, as the case may be,
shall set forth whether the Company will issue or deliver a fractional share
or units of a security upon conversion or exchange of a Security, or will
deliver its check for the value of the fractional share or units of a
security.

Section 1405. Taxes on Conversion or Exchange.

     The terms of a convertible or exchangeable Security, as the case may be,
shall state whether the Company will pay any documentary, stamp or similar
issue or transfer tax, due on the issue of shares or units of the security
issuable and whether upon the conversion or exchange the Holder will be
required to pay any such tax which is due because securities are issued in a
name other than that of such Holder.

Section 1406. Company to Provide Securities Issuable Upon Conversion or
Exchange.

     The Company shall reserve or otherwise provide for a sufficient amount of
its respective securities or securities of a third Person which would be
issuable upon the conversion or exchange of the Securities, including
reserving out of its respective authorized but unissued equity securities or
its equity securities held in treasury enough shares to permit the conversion
or exchange of the Securities.

     All shares of equity securities of the Company which may be issued upon
conversion or exchange of the Securities shall be fully paid and
nonassessable.

     The Company shall endeavor to comply with all securities laws regulating
the offer and delivery of shares or units of its respective securities issued
or delivered upon conversion or exchange of Securities and will endeavor to
list such shares or units on any national securities exchange on which such
shares or units are listed.

Section 1407. Adjustments.

     The terms of a convertible or exchangeable Security, as the case may be,
shall set forth the nature of mechanics for, and notice of, any adjustments in
the number or price of securities issuable upon conversion or exchange of the
Securities.

Section 1408. Valuation.

     The terms of a convertible or exchangeable Security, as the case may be,
shall set forth the method or methods for valuing the securities issuable upon
conversion or exchange of the Securities.

Section 1409. Reorganization of Company.

     The terms of a convertible or exchangeable Security, as the case may be,
shall set forth the rights, if any, of the Holders to convert or exchange
their Securities in the event that the Company is a party to a transaction
subject to Article 8 or a merger which reclassifies or changes


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the Company's securities into which the Securities are convertible or
exchangeable.

Section 1410. Trustee's Disclaimer.

     The Trustee has no duty or responsibility to determine when an adjustment
under this Article of the terms of the Securities should be made, how it
should be made or what it should be. The Trustee makes no representation as
to, and shall not be accountable for, the validity or value of any securities
issued upon conversion of or exchange for Securities. The Trustee shall not be
responsible for the failure of the Company to comply with this Article. Each
conversion and exchange agent other than the Company shall have the same
protection under this Section 1410 as the Trustee.

     1.9 Amendment to Exhibits A and C to the Indenture. Exhibits A and C are
amended by replacing references to "United States Treasury Regulation Section
1.165-12(c)(1)(v)" with references to "United States Treasury Regulation
Section 1.165-12(c)(1)(iv)."

     SECTION 2. MISCELLANEOUS

     2.1 Separability. In case any provision in this First Supplemental
Indenture shall be invalid, illegal or unenforceable, the validity, legality
and enforceability of the remaining provisions shall not in any way be
affected or impaired thereby.

     2.2 Continuance of Indenture. This First Supplemental Indenture
supplements the Indenture and shall be a part of and subject to all the terms
thereof. The Indenture, as supplemented by this First Supplemental Indenture,
shall continue in full force and effect.

     2.3 The Trustee. The Trustee shall not be responsible in any manner for
or in respect of, and makes no representations as to, the validity or
sufficiency of this First Supplemental Indenture, or for or in respect of the
recitals contained herein, all of which recitals are made by the Company
solely.

     2.4 Governing Law. This First Supplemental Indenture shall be governed by
and construed in accordance with the laws of the State of New York.

     2.5 Defined Terms. All capitalized terms used in this First Supplemental
Indenture that are defined in the Indenture, but not otherwise defined herein,
shall have the same meanings assigned to them in the Indenture.

     2.6 Counterparts. This First Supplemental Indenture may be executed in
any number of counterparts, each of which so executed shall be deemed to be an
original, but all such counterparts shall together constitute but one and the
same instrument.

     2.7 Effectiveness. This First Supplemental Indenture shall be effective
as of the date first above written, upon the execution and delivery hereof by
each of the parties hereto.

     JPMorgan Chase Bank hereby accepts the trusts in this First Supplemental
Indenture declared and provided, upon the terms and conditions hereinabove set
forth.

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     IN WITNESS WHEREOF, the parties hereto have caused this First
Supplemental Indenture to be duly executed by their respective
officers thereunto duly authorized, on the date or dates indicated
in the acknowlegments and as of the day and year first above written.


                                     KEYSPAN CORPORATION


                                     By: /s/ Gerald Luterman
                                         ---------------------------------
                                     Name:  Gerald Luterman
                                     Title: Executive Vice President and
                                            Chief Financial Officer

Attest:

/s/ Richard A. Rapp, Jr.
-----------------------------
    Richard A. Rapp, Jr.
    Secretary

                                     JPMORGAN CHASE BANK, as Trustee


                                     By: /s/ Francine Springer
                                         ---------------------------------
                                     Name:   Francine Springer
                                     Title:  Vice President

Attest:

/s/ Robert Peschler
--------------------------------
    Robert Peschler