EXHIBIT 2.1

                            SHARE PURCHASE AGREEMENT

             This AGREEMENT is dated as of January 29, 1998 by and among
        (i) Radley Services Ltd. ("Radley") and Peek Corporation ("PC"),
        on the one hand, (ii) ONIX Systems Inc., on the other hand
        ("Buyer"), and (iii) Thermo Power Corporation, a Massachusetts
        corporation ("Thermo").  Thermo, Radley and PC are sometimes
        referred to herein collectively as the Sellers. 

             WHEREAS, Sellers desire to sell all of the issued and
        outstanding shares of each of (i) Peek Measurement Ltd., a
        company organized under the laws of England ("PML"), (ii) Brandt
        Instruments Inc., a company organized under the laws of the State
        of Delaware ("Brandt") and (iii) Peek Measurement Inc., a company
        organized under the laws of the State of Texas ("PMI") to Buyer,
        and Buyer desires to purchase such shares from the Sellers;

             NOW, THEREFORE, in consideration of the premises and mutual
        promises and agreements set forth herein, the parties hereto
        hereby agree as follows:

             1.   Purchase and Sale of Shares.

                  (a)  PC hereby sells, assigns, transfers, conveys, and
        delivers to Buyer 100% of the issued and outstanding shares of
        capital stock of each of Brandt (the "Brandt Shares") and PMI
        (the "PMI Shares") and (ii) Radley hereby sells, assigns,
        transfers, conveys, and delivers to Buyer 100% of the issued and
        outstanding share capital of PML (the "PML Shares," collectively
        with the Brandt Shares and PMI Shares, the "Shares").  In
        consideration for the Shares, Buyer shall pay to Sellers an
        aggregate of $19,116,825 in cash (the "Purchase Price") plus
        interest on such amount for the period beginning November 6, 1997
        and ending on the date of payment of the Purchase Price, at a
        rate equal to the 90-day Commercial Paper Composite Rate for
        90-day maturities as reported by Merrill Lynch Capital Markets,
        as an average of the last five business days of the Buyer's
        latest fiscal quarter, plus 25 basis points, reset each quarter.
        The parties acknowledge and agree that the Purchase Price
        represents the sum of (i) the aggregate net tangible assets of
        PML, Brandt and PMI (collectively, the "Peek Measurement
        Business") (assumed to be $5,559,000) as of the date of Thermo's
        acquisition of the Peek Measurement Business as part of the
        acquisition on November 6, 1997, by Thermo of Peek plc (the "Peek
        plc Business"), plus (ii) a percentage of the total goodwill
        associated with Thermo's acquisition of the Peek plc Business
        equal to the total revenues of the Peek Measurement Business for
        the 1997 fiscal year relative to the total revenues of the Peek
        plc Business for such period, plus (iii) $1,038,825, representing
        the estimated tax liability of Thermo relating to the transfer of
        the Peek Measurement Business to Buyer.
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             2.   Further Assurances.  At the request of Buyer at any
        time on or after the date hereof, Sellers will execute and
        deliver such further instruments of transfer and conveyance and
        take such other action as Buyer reasonably may request
        effectively to assign and transfer to Buyer any of the Shares. 

             3.   Sellers' Representations and Warranties.  Each Seller
        represents and warrants that:

                  (a)  Organization and Existence.  Such Seller is a
        company organized and existing under the laws of its respective
        jurisdiction of organization.

                  (b)  Approval of Transactions.  Each Seller has
        obtained all necessary corporate authorizations and approvals,
        and has taken all actions required for the execution and delivery
        of this Agreement and the consummation of the transactions
        contemplated hereby.

                  (c)  No Conflict.  Neither the execution nor delivery
        of this Agreement, nor the consummation of the transactions
        herein contemplated, nor the fulfillment of or compliance with
        the terms and provisions hereof will (1) conflict with the
        charter documents or by-laws of such Seller, (2) violate any
        current provisions of law, administrative regulation, or court
        decree applicable to such Seller or (3) conflict with or result
        in a breach of any of the terms, conditions or provisions of or
        constitute default under any material agreement or instrument to
        which such Seller, or any Peek Measurement Business entity, is a
        party or by which each is bound.

                  (d)  Ownership of Assets and Shares; Authority to
        Transfer.  The Shares are not encumbered and are freely
        transferable by the respective Seller.  PC holds good and
        marketable title to the Brandt Shares and the PMI Shares and no
        third party is entitled to claim any right thereto or make any
        claim thereon.  Radley holds good and marketable title to the PML
        Shares and no third party is entitled to claim any right thereto
        or make any claim thereon. The transfer of the Shares to Buyer
        pursuant to this Agreement will vest in Buyer title to the
        Shares, free and clear of all liens, claims, equities, options,
        calls, voting trusts, agreements, commitments and encumbrances
        whatsoever.  

             4.   Buyer's Representations and Warranties.

                  (a)  Organization and Existence.  The Buyer is a
        company organized and existing under the laws of its jurisdiction
        of organization.

                  (b)  Approval of Transactions.  The Buyer has obtained
        all necessary corporate authorizations and approvals, and has
        taken all actions required for the execution and delivery of this

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        Agreement and the consummation of the transactions contemplated
        hereby.

                  (c)  No Conflict.  Neither the execution nor delivery
        of this Agreement, nor the    consummation of the transactions
        herein contemplated, nor the fulfillment of or compliance with
        the terms and provisions hereof will (1) conflict with the
        charter documents or by-laws of the Buyer, (2) violate any
        current provisions of law, administrative regulation, or court
        decree applicable to the Buyer or (3) conflict with or result in
        a breach of any of the terms, conditions or provisions of or
        constitute default under any material agreement or instrument to
        which the Buyer is a party or by which it is bound.

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             5.   Indemnification.

                  (a)  Sellers jointly and severally agree to indemnify
        and hold harmless Buyer from any and all damages, losses,
        liabilities, costs and expenses (including, without limitation,
        settlement costs and any reasonable legal, accounting or other
        expenses for investigating or defending any actions or threatened
        actions) incurred by Buyer as a result of (i) the inaccuracy of
        any representation or warranty contained in Section 3 hereof or
        (ii) the breach by Sellers of any provision hereof.

                  (b)  Buyer agrees to indemnify and hold harmless
        Sellers from any and all damages, losses, liabilities, costs and
        expenses (including, without limitation, settlement costs and any
        reasonable legal, accounting or other expenses for investigating
        or defending any actions or threatened actions) incurred by
        Sellers as a result of (i) the inaccuracy of any representation
        or warranty contained in Section 4 hereof or (ii) the breach by
        Buyer of any provision hereof.

                  (c)  Whenever any claim shall arise for indemnification
        hereunder, the party seeking indemnification (the "Indemnified
        Party") shall promptly notify the other party or parties from
        whom indemnification is sought (as the case may be, the
        "Indemnifying Party") of the claim and, when known, the facts
        constituting the basis for such claim.  In the event of any such
        claim for indemnification hereunder resulting from or in
        connection with any claim or legal proceedings by a third party,
        the notice to the Indemnifying Party shall specify, if known, the
        amount or an estimate of the amount of the liability arising
        therefrom.  The Indemnified Party shall not settle or compromise
        any claim by a third party for which the Indemnified Party is
        entitled to indemnification hereunder without the prior consent
        of the Indemnifying Party, unless suit shall have been instituted
        against the Indemnified Party and the Indemnifying Party shall
        not have taken control of such suit after notification thereof as
        provided in Section 5(d) of this Agreement.

                  (d)  In connection with any claim giving rise to
        indemnity hereunder resulting from or arising out of any claim or
        legal proceeding by a person who is not a party to this
        Agreement, the Indemnifying Party at its sole cost and expense
        may, upon notice to the Indemnified Party, assume the defense of
        any such claim or legal proceeding if it acknowledges to the
        Indemnified Party its obligations to indemnify the Indemnified
        Party with respect to all elements of such claim.  The
        Indemnified Party shall be entitled to participate in (but not
        control) the defense of any such action, with its counsel and at
        its own expense.  If the Indemnifying Party does not assume the
        defense of any such claim or litigation resulting therefrom
        within 30 days after the date the Indemnifying Party is notified
        of such claim pursuant to Paragraph 5(c) hereof, (i) the
        Indemnified Party may defend against such claim or litigation,

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        after giving notice of the same to the Indemnifying Party, on
        such terms as are appropriate in the Indemnified Party's
        reasonable judgment, and (ii) the Indemnifying Party shall be
        entitled to participate in (but not control) the defense of such
        action, with its counsel and at its own expense.

             6.   Effective Date.  The transfer of the Shares shall be
        deemed to be effective as of November 6, 1997.

             7.   Captions.  The captions and headings to the various
        sections, paragraphs and exhibits of this Agreement are for
        convenience of reference only and shall not affect or control the
        meaning or interpretation of any of the provisions of this
        Agreement.

             8.   Integration.  This Agreement contains the entire
        understanding of the parties hereto with respect to the subject
        matter contained herein.

             9    Notices and Communications.  Any notice or other
        communication shall be in writing and shall be personally
        delivered, or sent by overnight or second day courier or by first
        class mail, return receipt requested, to the party to whom such
        notice or other communication is to be given or made at such
        party's address set forth below, or to such other address as such
        party shall designate by written notice to the other party as
        follows:

             If to Sellers or Thermo Power Corporation:

                  Thermo Power Corporation
                  c/o Thermo Electron Corporation
                  81 Wyman Street
                  P.O. Box 9046
                  Waltham, MA  02254-9046
                  Attn.: General Counsel


             If to Buyer:

                  ONIX Systems Inc.
                  c/o Thermo Electron Corporation
                  81 Wyman Street
                  P.O. Box 9046
                  Waltham, MA  02254-9046
                  Attn.: General Counsel

        provided that any notice of change of address, and any notice or
        other communication given otherwise than as specified above shall
        be effective only upon receipt; and further that any presumption
        of receipt by the addressee shall be inoperable during the period
        of any interruption in Postal Service.

             10.  Survival of Representations and Warranties.  All
        representations and warranties made by Sellers or Buyer in this

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        Agreement shall survive the execution and delivery of this
        Agreement.

             11.  Governing Law; Assignment.  This Agreement is to be
        construed, interpreted, applied and governed in all respects in
        accordance with the laws of the Commonwealth of Massachusetts,
        without regard to its conflict of laws provisions, is to take
        effect as a sealed instrument, is binding upon and inures to the
        benefit of the parties hereto and their respective successors and
        assigns and may be canceled, modified or amended only by a
        written instrument executed by Thermo, Sellers and Buyer.  No
        party hereto may assign its rights hereunder without prior
        written consent of the other party.

             12.  Guaranty.  Thermo hereby unconditionally guarantees all
        of the obligations of the other Sellers under this Agreement.

             13.  Counterparts.  This Agreement may be executed in
        counterparts, all of which together shall for all purposes
        constitute one Agreement, binding on the parties hereto
        notwithstanding that such parties have not signed the same
        counterpart.  


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             IN WITNESS WHEREOF, the parties hereto have executed this
        Agreement as of the date and year first above written.

        SELLERS:

        RADLEY SERVICES LTD.               PEEK CORPORATION

        By: J. Timothy Corcoran            By: J. Timothy Corcoran
            ----------------------------       --------------------------

        Title: Authorized Signatory        Title: Chariman
               -------------------------          -----------------------


        BUYER:                        THERMO:

        ONIX SYSTEMS INC.             THERMO POWER CORPORATION
             
        By: William J. Zolner           By: J. Timothy Corcoran
            -----------------------         ---------------------
              
        Title: President & CEO          Title: President & CEO
               --------------------            ------------------