Exhibit 2.5


                          SECOND AMENDMENT TO SUBLEASE



             THIS SECOND AMENDMENT TO SUBLEASE (this "Amendment") is
        entered into as of October 10, 1997, by and between TMO, INC.,
        having an address at 81 Wyman Street, Waltham, Massachusetts
        02254 ("Landlord"), and THERMO TERRATECH INC., having an address
        at 81 Wyman Street, Waltham, Massachusetts 02254 ("Tenant").  

                              W I T N E S S E T H:

             WHEREAS, pursuant to the terms of that certain Agreement of
        Lease dated as of December 31, 1985 (as amended, the
        "Overlease"), by and between W & C Investment Co.
        ("Overlandlord"), successor-in-interest to Claridge Properties
        Ltd., and Landlord, successor-in-interest to Thermo Electron
        Corporation, Overlandlord currently leases to Landlord certain
        premises known and numbered as 12068 Market Street, Livonia,
        Michigan, and more particularly described in the Overlease (the
        "Demised Premises"); and 

             WHEREAS, pursuant to the terms of that certain Sublease
        dated as of March 30, 1986 (as amended, the "Sublease"), by and
        between Landlord and Tenant, successor-in-interest to
        Holcroft/Loftus, Inc., Landlord currently subleases to Tenant the
        Demised Premises; and 

             WHEREAS, Landlord and Tenant desire to amend the Sublease as
        more particularly set forth herein;

             NOW, THEREFORE, in consideration of the mutual covenants set
        forth herein, and for other good and valuable consideration, the
        receipt and sufficiency of which are hereby acknowledged, the
        parties hereto agree as follows:

             1.   Section 6.6 of the Sublease is hereby amended to
        incorporate by reference into the Sublease the provisions of
        Article 30 of the Overlease.

             2.   The following new Article is hereby added to the
        Sublease:

                  "Article 9.    Option to Extend.

                  Section  9.1.    Provided that Tenant shall not be in
        default of its obligations under this Sublease, Tenant shall have
        an option to extend the Term of this Sublease for one (1)
        additional period of five (5) years (the "Renewal Period"), which
        option shall be exercisable by written notice to Landlord given
        no less than thirteen (13) months prior to the expiration of the
PAGE

        then current Term.  Upon receipt of such notice, Landlord shall
        exercise its corresponding option to renew the Overlease.  All of
        the terms, covenants and provisions of this Sublease shall apply
        to such Renewal Period, except that the annual fixed rental
        payable with respect to such Renewal Period shall be equal to the
        annual Fixed Rent payable to Overlandlord under Article 30 of the
        Overlease.  In the event that Tenant elects to exercise its
        option to extend under this Section 9.1, Tenant shall be
        responsible for the payment of all costs payable by the lessee
        under Section 30.04 of the Overlease.  During the Renewal Period,
        all references in this Sublease to the Term shall be deemed to
        mean the original Term as extended by the Renewal Period.  Tenant
        shall have no further right to extend the Term of this Sublease
        following the expiration of the Renewal Period."

             3.   Except as specifically herein provided, all of the
        terms, provisions, covenants and conditions of the Sublease are
        hereby ratified and confirmed and shall continue in full force
        and effect.  Any capitalized term not defined herein shall have
        the meaning ascribed to it under the Sublease.

             4.   The individuals executing this Amendment hereby
        represent and warrant that they are empowered and duly authorized
        to so execute this Amendment on behalf of the parties they
        represent. 

             IN WITNESS WHEREOF, the parties hereto have caused this
        Amendment to be executed as a sealed instrument as of the date
        first above written.

                                           LANDLORD:

                                           TMO, INC., 
                                           a Delaware corporation


                                           By:    /s/Sandra L. Lambert
                                           Name:  Sandra L. Lambert
                                           Title: Secretary



                                           TENANT:

                                           THERMO TERRATECH INC.,
                                           a Delaware corporation

                                           By:    /s/ John P. Appleton
                                           Name:  John P. Appleton
                                           Title: Chief Executive Officer