EXHIBIT 5.1
                            [ROPES & GRAY LETTERHEAD]

                                January 28, 2000

Eastern Enterprises
9 Riverside Road
Weston, MA 02493

Re:  Eastern Enterprises

Ladies and Gentlemen:

     This opinion is furnished to you in connection with a registration
statement on Form S-4 (the "Registration Statement"), filed with the Securities
and Exchange Commission under the Securities Act of 1933, as amended, for the
registration of certain shares of Common Stock, $1.00 par value (the "Shares"),
of Eastern Enterprises, a Massachusetts business trust (the "Company"), to be
issued pursuant to an Agreement and Plan of Reorganization dated as of July 14,
1999, as amended by Amendment No. 1 to Agreement and Plan of Reorganization
dated as of November 4, 1999 (the "Merger Agreement"), by and among the Company,
EE Acquisition Company, Inc., a New Hampshire corporation, and EnergyNorth,
Inc., a New Hampshire corporation.

     We have acted as counsel for the Company in connection with the Merger
Agreement and the proposed issuance of the Shares thereunder. For purposes of
this opinion, we have examined and relied upon such documents, records,
certificates and other instruments as we have deemed necessary.

     We express no opinion as to the applicability of, compliance with or effect
of Federal law or the law of any jurisdiction other than The Commonwealth of
Massachusetts and the corporate laws of the State of Delaware.

     Based on the foregoing, we are of the opinion that the Shares have been
duly authorized and, when the Shares have been issued and delivered in
accordance with the terms of the Merger Agreement, the Shares will be validly
issued, fully paid and non-assessable.

     We hereby consent to your filing this opinion as an exhibit to the
Registration Statement and to the use of our name therein.

     It is understood that this opinion is to be used only in connection with
the Registration Statement while it is in effect and may not be relied upon for
any other purpose.

                              Very truly yours,

                              /s/ ROPES & GRAY

                              Ropes & Gray