EXHIBIT 99(a)
 
PROXY

                        THE BROOKLYN UNION GAS COMPANY

        THIS PROXY IS SOLICITED ON BEHALF OF THE BOARD OF DIRECTORS FOR
       THE SPECIAL MEETING OF SHAREHOLDERS TO BE HELD ON AUGUST 7, 1997

The undersigned hereby appoints Donald H. Elliott, Alan H. Fishman and Edward D.
Miller, and each of them with full power to act alone, the true and lawful
attorneys in fact and proxies of the undersigned to vote all shares of Common
Stock of THE BROOKLYN UNION GAS COMPANY, a New York corporation (the "Company"),
held by the undersigned, with full power of substitution, with the same force
and effect as the undersigned would be entitled to vote if personally present,
at the Special Meeting of Shareholders of the Company to be held at the Opera
House, Brooklyn Academy of Music, 30 Lafayette Avenue, Brooklyn, New York 11217,
on August 7, 1997, at 3:00 p.m. (local time), and at any and all adjournments or
postponements thereof.

PLEASE MARK, SIGN, DATE AND RETURN THIS PROXY CARD PROMPTLY, USING THE ENCLOSED
ENVELOPE.

                                                                   [SEE REVERSE
                                                                        SIDE]

 
[X] Please mark 
    your votes as in this 
    example


- --------------------------------------------------------------------------------
THE COMPANY'S BOARD OF DIRECTORS RECOMMENDS A VOTE "FOR" THE ADOPTION OF BOTH
PROPOSALS
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1. Adoption of the Amended and Restated Agreement         FOR  AGAINST  ABSTAIN 
and Plan of Exchange and Merger, dated as of              [_]    [_]      [_]
June 26, 1997 between Long Island Lighting Company 
and the Company.


2. Adoption of the Amended and Restated Agreement         FOR  AGAINST  ABSTAIN 
and Plan of Exchange, dated as of June 26, 1997           [_]    [_]      [_]
between KeySpan Energy Corporation and the Company.


THIS PROXY, WHEN PROPERLY EXECUTED, WILL BE VOTED IN THE MANNER DIRECTED HEREIN.
IF THIS PROXY IS SUBMITTED, BUT NO DIRECTIONS ARE MADE, THIS PROXY WILL BE VOTED
"FOR" THE APPROVAL AND ADOPTION OF THE BROOKLYN UNION/LILCO AGREEMENT AND THE
KEYSPAN EXCHANGE AGREEMENT.

The undersigned hereby acknowledges receipt of the Notice of Special Meeting of
Shareholders and the related Joint Proxy Statement/Prospectus furnished
herewith.

Date:                                                      , 1997
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Signature:
          -------------------------------------------------

Signature(s)(if held jointly):
                               ---------------------------- 

Title or Authority:
                   ----------------------------------------


IMPORTANT: Please sign your name exactly as it appears hereon. When signing as
           attorney, agent, executor, administrator, trustee, guardian or
           corporate officer, please give your full title as such. Each joint
           owner should sign the proxy. If executed by a partnership, this proxy
           should be signed by an authorized partner.