Exhibit 10.42
                              THERMO TERRATECH INC.

                         STOCK HOLDINGS ASSISTANCE PLAN

        SECTION 1.   Purpose.

             The purpose of this Plan is to benefit Thermo TerraTech Inc.
        (the "Company") and its stockholders by encouraging Key Employees
        to acquire and maintain share ownership in the Company, by
        increasing such employees' proprietary interest in promoting the
        growth and performance of the Company and its subsidiaries and by
        providing for the implementation of the Guidelines.  

        SECTION 2.     Definitions.

             The following terms, when used in the Plan, shall have the
        meanings set forth below:

             Committee:   The Human Resources Committee of the Board of
        Directors of the Company as appointed from time to time.

             Common Stock:   The common stock of the Company and any
        successor thereto.

             Company:   Thermo TerraTech Inc., a Delaware corporation.

             Guidelines:  The Stock Holdings Guidelines for Key Employees
        of the Company, as established by the Committee from time to
        time.

             Key Employee:   Any employee of the Company or any of its
        subsidiaries, including any officer or member of the Board of
        Directors who is also an employee, as designated by the
        Committee, and who, in the judgment of the Committee, will be in
        a position to contribute significantly to the attainment of the
        Company's strategic goals and long-term growth and prosperity.

             Loans:   Loans extended to Key Employees by the Company
        pursuant to this Plan.

             Plan:   The Thermo TerraTech Inc. Stock Holdings Assistance
        Plan, as amended from time to time.

        SECTION 3.     Administration.

             The Plan and the Guidelines shall be administered by the
        Committee, which shall have authority to interpret the Plan and
        the Guidelines and, subject to their provisions, to prescribe,
        amend and rescind any rules and regulations and to make all other
        determinations necessary or desirable for the administration
        thereof.  The Committee's interpretations and decisions with
        regard to the Plan and the Guidelines and such rules and
        regulations as may be established thereunder shall be final and
        conclusive.  The Committee may correct any defect or supply any
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        omission or reconcile any inconsistency in the Plan or the
        Guidelines, or in any Loan in the manner and to the extent the
        Committee deems desirable to carry it into effect.  No member of
        the Committee shall be liable for any action or omission in
        connection with the Plan or the Guidelines that is made in good
        faith.

        SECTION 4.     Loans and Loan Limits.

             The Committee has determined that the provision of Loans
        from time to time to Key Employees in such amounts as to cause
        such Key Employees to comply with the Guidelines is, in the
        judgment of the Committee, reasonably expected to benefit the
        Company and authorizes the Company to extend Loans from time to
        time to Key Employees in such amounts as may be requested by such
        Key Employees in order to comply with the Guidelines.  Such Loans
        may be used solely for the purpose of acquiring Common Stock
        (other than upon the exercise of stock options or under employee
        stock purchase plans) in open market transactions or from the
        Company.

             Each Loan shall be full recourse and evidenced by a
        non-interest bearing promissory note substantially in the form
        attached hereto as Exhibit A (the "Note") and maturing in
        accordance with the provisions of Section 6 hereof, and
        containing such other terms and conditions, which are not
        inconsistent with the provisions of the Plan and the Guidelines,
        as the Committee shall determine in its sole and absolute
        discretion.

        SECTION 5.     Federal Income Tax Treatment of Loans.

             For federal income tax purposes, interest on Loans shall be
        imputed on any interest free Loan extended under the Plan.  A Key
        Employee shall be deemed to have paid the imputed interest to the
        Company and the Company shall be deemed to have paid said imputed
        interest back to the Key Employee as additional compensation.
        The deemed interest payment shall be taxable to the Company as
        income, and may be deductible to the Key Employee to the extent
        allowable under the rules relating to investment interest.  The
        deemed compensation payment to the Key Employee shall be taxable
        to the employee and deductible to the Company, but shall also be
        subject to employment taxes such as FICA and FUTA.

        SECTION 6.     Maturity of Loans.

             Each Loan to a Key Employee hereunder shall be due and
        payable on demand by the Company.  If no such demand is made,
        then each Loan shall mature and the principal thereof shall
        become due and payable in five equal annual installments
        commencing on the first anniversary date of the making of such
        Loan.  Each Loan shall also become immediately due and payable in
        full, without demand, upon  the occurrence of any of the events
        set forth in the Note; provided that the Committee may, in its

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        sole and absolute discretion, authorize an extension of the time
        for repayment of a Loan upon such terms and conditions as the
        Committee may determine.

        SECTION 7.     Amendment and Termination of the Plan.

             The Committee may from time to time alter or amend the Plan
        or the Guidelines in any respect, or terminate the Plan or the
        Guidelines at any time.  No such amendment or termination,
        however, shall alter or otherwise affect the terms and conditions
        of any Loan then outstanding to Key Employee without such Key
        Employee's written consent, except as otherwise provided herein
        or in the promissory note evidencing such Loan.

        SECTION 8.     Miscellaneous Provisions.

             (a)  No employee or other person shall have any claim or
        right to receive a Loan under the Plan, and no employee shall
        have any right to be retained in the employ of the Company due to
        his or her participation in the Plan.

             (b)  No Loan shall be made hereunder unless counsel for the
        Company shall be satisfied that such Loan will be in compliance
        with applicable federal, state and local laws.

             (c)  The expenses of the Plan shall be borne by the Company.

             (d)  The Plan shall be unfunded, and the Company shall not
        be required to establish any special or separate fund or to make
        any other segregation of assets to assure the making of any Loan
        under the Plan.

             (e)  Except as otherwise provided in Section 7 hereof, by
        accepting any Loan under the Plan, each Key Employee shall be
        conclusively deemed to have indicated his acceptance and
        ratification of, and consent to, any action taken under the Plan
        or the Guidelines by the Company, the Board of Directors of the
        Company or the Committee.

             (f)  The appropriate officers of the Company shall cause to
        be filed any reports, returns or other information regarding
        Loans hereunder, as may be required by any applicable statute,
        rule or regulation.

        SECTION 9.     Effective Date.

             The Plan and the Guidelines shall become effective upon
        approval and adoption by the Committee.

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                                                          EXHIBIT A


                              THERMO TERRATECH INC.

                                 Promissory Note



        $_________                                                       
                                                Dated:____________


             For value  received, ________________,  an individual  whose
        residence is located at _______________________ (the "Employee"),
        hereby promises to pay to Thermo TerraTech Inc. (the  "Company"),
        or assigns, ON DEMAND, but in any case on or before [insert  date
        which  is  the  fifth  anniversary  of  date  of  issuance]  (the
        "Maturity Date"), the  principal sum  of [loan  amount in  words]
        ($_______), or such part thereof as then remains unpaid,  without
        interest.   Principal shall  be payable  in lawful  money of  the
        United States of America, in immediately available funds, at  the
        principal office of  the Company or  at such other  place as  the
        Company may  designate  from  time  to time  in  writing  to  the
        Employee. 

              Unless the Company has already made a demand for payment in
        full of this Note, the Employee  agrees to repay the Company,  on
        each of the first four anniversary  dates of the date hereof,  an
        amount equal to 20% of the initial principal amount of the  Note.
        Payment of the final 20% of  the initial principal amount, if  no
        demand has been made by the Company, shall be due and payable  on
        the Maturity Date.

             This Note may be prepaid at  any time or from time to  time,
        in whole  or  in part,  without  any  premium or  penalty.    The
        Employee acknowledges and agrees that the Company has advanced to
        the Employee the principal  amount of this  Note pursuant to  the
        Company's Stock Holdings Assistance Plan, and that all terms  and
        conditions of such Plan are incorporated herein by reference.  

             The unpaid principal amount of this Note shall be and become
        immediately due  and payable  without notice  or demand,  at  the
        option of  the  Company,  upon  the  occurrence  of  any  of  the
        following events:

                  (a)  the termination of the Employee's employment  with
             the Company, with or without cause, for any reason or for no
             reason;

                  (b)  the death or disability of the Employee;

                  (c)  the failure  of the  Employee to  pay his  or  her
             debts as they  become due, the  insolvency of the  Employee,

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             the filing by or against the Employee of any petition  under
             the United  States Bankruptcy  Code (or  the filing  of  any
             similar  petition   under   the  insolvency   law   of   any
             jurisdiction),  or  the  making   by  the  Employee  of   an
             assignment or trust mortgage for the benefit of creditors or
             the appointment of  a receiver, custodian  or similar  agent
             with respect  to,  or  the  taking by  any  such  person  of
             possession of, any property of the Employee; or

                  (d)  the issuance of any writ of attachment, by trustee
             process or otherwise, or any restraining order or injunction
             not removed, repealed or  dismissed within thirty (30)  days
             of issuance, against or affecting the person or property  of
             the Employee or any liability or obligation of the  Employee
             to the Company.

             In case any payment  herein provided for  shall not be  paid
        when due,  the Employee  further  promises to  pay all  costs  of
        collection, including all reasonable attorneys' fees.

             No  delay  or  omission  on  the  part  of  the  Company  in
        exercising any right hereunder shall operate as a waiver of  such
        right or of any other right of the Company, nor shall any  delay,
        omission or waiver  on any  one occasion be  deemed a  bar to  or
        waiver of the  same or any  other right on  any future  occasion.
        The  Employee  hereby  waives  presentment,  demand,  notice   of
        prepayment,  protest  and  all  other  demands  and  notices   in
        connection with the delivery, acceptance, performance, default or
        enforcement of this Note.  The undersigned hereby assents to  any
        indulgence  and  any  extension  of  time  for  payment  of   any
        indebtedness  evidenced  hereby  granted  or  permitted  by   the
        Company.  

             This Note  has been  made pursuant  to the  Company's  Stock
        Holdings Assistance Plan and shall  be governed by and  construed
        in accordance  with, such  Plan  and the  laws  of the  State  of
        Delaware and shall have the effect of a sealed instrument.


                                      _______________________________

                                      Employee Name: _________________


        ________________________
        Witness