UNITED STATES
                      SECURITIES AND EXCHANGE COMMISSION
                            WASHINGTON, D.C. 20549

                                 SCHEDULE 14A 

          Proxy Statement Pursuant to Section 14(a) of the Securities
                    Exchange Act of 1934 (Amendment No.  )
        
Filed by the Registrant [X]

Filed by a Party other than the Registrant [_] 

Check the appropriate box:

[_]  Preliminary Proxy Statement         

[_]  CONFIDENTIAL, FOR USE OF THE
     COMMISSION ONLY (AS PERMITTED BY
     RULE 14A-6(E)(2))

[_]  Definitive Proxy Statement 

[X]  Definitive Additional Materials 

[_]  Soliciting Material Pursuant to (S) 240.14a-11(c) or (S) 240.14a-12

                            MarketSpan Corporation
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               (Name of Registrant as Specified In Its Charter)


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   (Name of Person(s) Filing Proxy Statement, if other than the Registrant)

   
Payment of Filing Fee (Check the appropriate box):

[X]  No fee required.

[_]  Fee computed on table below per Exchange Act Rules 14a-6(i)(4) and 0-11.

   
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     (2) Aggregate number of securities to which transaction applies:

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     (3) Per unit price or other underlying value of transaction computed
         pursuant to Exchange Act Rule 0-11 (set forth the amount on which
         the filing fee is calculated and state how it was determined):

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[_]  Fee paid previously with preliminary materials.
     
[_]  Check box if any part of the fee is offset as provided by Exchange
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     (4) Date Filed:

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Notes:






Reg. (S) 240.14a-101.

SEC 1913 (3-99)



 
[KeySpan Logo]                           One MetroTech Center
                                         Brooklyn, New York 11201-3850



[date]

Dear Shareholder:

We previously sent you proxy materials relating to our Annual Meeting of
Shareholders to be held on May 20, 1999.

According to our tabulator's latest records, they have not received your proxy.
In order to have as great a representation as possible at the meeting, we urge
you to give this your immediate consideration.  The proposals to be voted on are
important.

Please complete and return the enclosed duplicate proxy using the postpaid
return envelope or give a proxy by telephone by calling 1-800-574-6864.  Have
your proxy card in hand when you call and follow the simple instructions.  You
do not have to mail your proxy card if you vote by telephone.

Thank you for your consideration.

Sincerely,