DATED November 4, 1996
                             ----------------------






             (1)  SID INSTRUMENTS INC.

             (2)  ATI ACQUISITION CORP.

             (3)  THERMO INSTRUMENT SYSTEMS INC.







                   __________________________________________

                                    AGREEMENT
                     for the sale and purchase of the whole
                         of the issued share capital of
                            Thermo Elemental Limited
                  ____________________________________________

















                                 WARNER CRANSTON
                                 Pickfords Wharf
                                  Clink Street
                                 London SE1 9DG

                               Tel: 0171 403 2900
                               Fax: 0171 403 4221
                              Ref: SXC/TE/1686-40-7
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        THIS AGREEMENT is made the 4th day of November                   

                 1996


        BETWEEN:


        (1)  SID INSTRUMENTS INC. (the "Vendor") a Delaware corporation
             whose principal office is at 81 Wyman Street, Waltham, MA
             02254, USA; 

        (2)  ATI ACQUISITION CORP. (the "Purchaser") a Delaware
             corporation whose principal office is at 81 Wyman Street,
             Waltham, MA 02254, USA; and

        (3)  THERMO INSTRUMENT SYSTEMS INC. ("Thermo") a Delaware
             corporation whose principal office is at 81 Wyman Street,
             Waltham, MA 02254, USA.

        WHEREAS:

        (A)  Thermo Elemental Limited ("the Company") is a private
             company incorporated with limited liability in England
             further particulars of which are set out in Schedule 2. 

        (B)  The Vendor has agreed to sell and the Purchaser has agreed
             to buy the Shares (as defined) on the terms and subject to
             the conditions contained in this Agreement.

        AGREED as follows:

        1.   INTERPRETATION

        1.1  In this Agreement and the Schedules to it the following
             expressions shall, unless the context otherwise requires,
             have the following meanings:

             "the Effective Date"               4 November 1996;

             "the Shares"                  the shares in the capital of
                                           the Company set out in Column
                                           (2) of Schedule 1; 

        1.2  The headings in this Agreement are for ease of reference
             only and shall not be taken into account in construing this
             Agreement.  

        1.3  References to Clauses and Schedules are to clauses and
             schedules of this Agreement.

        2.   SALE AND PURCHASE
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        2.1  The Vendor agrees to sell with full title guarantee, the
             Shares and the Purchaser agrees to purchase the Shares with
             effect on and from the Effective Date free from any liens,
             claims, charges, encumbrances and equities and together with
             all rights of any nature whatsoever now or after the date of
             this Agreement attaching or accruing to them. 

        2.2  The aggregate consideration for the purchase of the Shares
             shall be the sum set out in Column (3) of Schedule 1 receipt
             of which the Vendor hereby acknowledges.  The Purchaser and
             Vendor acknowledge and agree that such Consideration
             represents the sum of (i) the net tangible assets of the
             Company assumed to be $8,418,000) as of the date of Thermo's
             acquisition of the Shares as part of the acquisition on
             March 29, 1996 by Thermo and its subsidiaries of certain
             businesses of Fisons plc (the "Fisons Businesses") pursuant
             to the Amended and Restated Asset and Stock Purchase
             Agreement dated as of March 29, 1996 among Thermo, Thermo
             Electron Corporation and Fisons plc (the "Restated
             Agreement"), plus (ii) a percentage of the total goodwill
             associated with Thermo's acquisition of the Fisons
             Businesses equal to the sales of the Company for the 1994
             and 1995 fiscal years relative to the total sales of the
             Fisons Businesses for such years (the "Company Percentage"),
             plus (iii) the Company Percentage of the total costs
             incurred by Thermo in acquiring the Fisons Businesses and in
             restructuring the sales and service organization of the
             Fisons Businesses (the "Restructuring Costs").  The parties
             acknowledge that the purchase price paid by Thermo for the
             Fisons Businesses is subject to a post-closing adjustment
             based on the difference between the value of the net
             tangible assets of the Fisons Businesses as shown on the
             closing balance sheet dated as of March 29, 1996 (the
             "Closing Balance Sheet") and the target net tangible asset
             value provided for in the Restated Agreement.  In the event
             of any such adjustment, the Consideration shall be
             recalculated in accordance with the second sentence of this
             paragraph to account for (A) any adjustment in the net
             tangible assets (other than cash) of the Company as shown on
             the Closing Balance Sheet from $8,418,000 and (B) any
             adjustment in the total goodwill associated with Thermo's
             acquisition of the Fisons Businesses.  In addition, the
             Consideration shall be subject to recalculation in
             accordance with the second sentence of this paragraph in the
             event that the Restructuring Costs incurred are less than
             $1,378,000.  If the recalculation made pursuant to this
             paragraph results in an increase in the Consideration, the
             Purchaser shall pay the amount of such increase to the
             Vendor, and if any such recalculation results in a decrease
             in the Consideration, the Vendor shall pay the amount of
             such decrease to the Purchaser.  Any payment made pursuant
             to the preceding sentence shall be made within ten days
             after the Closing Balance Sheet has become final (in the
             case of any adjustment related to the Closing Balance Sheet)
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             and no later than March 29, 1997 (in the case of an
             adjustment related to the Restructuring Costs) and shall
             also be accompanied by interest from the date hereof
             calculated as provided in Section 4.1 of the Restated
             Agreement.

        3.   FURTHER ASSURANCE

             The Vendor shall on or at any time after the date of this
             Agreement execute and do all such deeds, documents, acts and
             things as the Purchaser shall reasonably require to give
             effect to this Agreement.

        4.   WARRANTIES

        4.1  The Vendor represents, warrants and undertakes to and with
             the Purchaser in the terms contained in Schedule 3. 

        4.2  The representations, warranties and undertakings contained
             in Schedule 3 shall continue in full force and effect after
             the date of this Agreement.

        5.   COMPLETION

             Completion of the sale and purchase of the Shares shall take
             place on the date of this Agreement at such time and place
             as the parties shall agree when:

             (a)  the Vendor shall hand to the Purchaser duly executed
                  transfers in favor of the Purchaser and the share
                  certificates in respect of the Shares;

             (b)  the Vendor shall, if required, hand to the Purchaser
                  the certificate of incorporation, statutory books and
                  common seal of the Company;

             (c)  the Purchaser shall pay the consideration in accordance
                  with Clause 2.2.

        6.   INDEMNITY

        6.1  The Vendor agrees to indemnify and hold harmless the
             Purchaser 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 the Purchaser as a result of
             (i) the inaccuracy of any representation or warranty
             contained in Schedule 3 hereof; (ii) the breach by the
             Vendor of any provision hereof; or (iii) any third party
             claim arising due to the act of omission of the Vendor or
             the Company from March 29, 1996 and prior to the date
             hereof.
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        6.2  The Purchaser agrees to indemnify and hold harmless the
             Vendor 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 the Vendor as a result of the breach by
             the Purchaser of any provision hereof.

        6.3  Whenever any claim shall arise or indemnification under this
             Agreement, the party seeking indemnification (the
             "Indemnified Party"), shall promptly notify the other party
             (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 proceedings have been
             commenced against the Indemnified Party and the Indemnifying
             Party shall not have taken control of such proceedings after
             notification thereof as provided in Clause 6.4 of this
             Agreement.

        6.4  In connection with any claim giving rise to indemnity
             hereunder resulting from or arising out of a claim or legal
             proceedings by a person who is not a party to this
             Agreement, the Indemnifying Party at its sole cost and
             expense may, on notice to the Indemnified party, assume the
             defense of any such claim or legal proceedings 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 Solicitors of its own choice and 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 Clause 8.1 hereof, (i)
             the Indemnified Party may defend against such claim or
             litigation, 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 Solicitors of
             its own choice and at its own expense.
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        7.   GENERAL

        7.1  The provisions of this Agreement shall enure to the benefit
             of the successors and assigns of the Vendor and the
             Purchaser.

        8.   NOTICES

        8.1  A notice or other communication under or in connection with
             this Agreement shall be in writing and shall be delivered
             personally or sent by first class pre-paid recorded delivery
             post or by fax to the party due to receive the notice or
             communication at its address set out in this Agreement or
             such other address as either party may specify by notice in
             writing to the other.

        8.2  In the absence of evidence of earlier receipt, a notice or
             communication is deemed given:

             8.2.1     if delivered personally, when left at the address
             referred to in the introduction hereto;

             8.2.2     if sent by post, the second business day after its
             posting;

             8.2.3     if sent by fax, on completion of its transmission.

        9.   GUARANTEE

             Thermo hereby unconditionally guarantees the obligations of
        the Vendor arising under this Agreement.
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        10.  GOVERNING LAW

             This Agreement shall be governed by and construed in all
             respects in accordance with English Law and the parties
             agree to submit to the exclusive jurisdiction of the English
             Courts as regards any claim or matter arising in relation to
             this Agreement.
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                                   SCHEDULE 1

                     Particulars of Shares and Consideration

                (1)                  (2)                         (3)
        Name of the Company    Particulars of Shares       Consideration
        -------------------    ---------------------       -------------

        Thermo Elemental     2 Ordinary Shares              $18,897,000
        Limited              of 1 British Pounds 
                             Sterling each
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                                   SCHEDULE 2
                           Particulars of the Company


        Date of Incorporation:             31/01/96

        Registered Office:            Pickfords Wharf
                                      Clink Street
                                      London SE1 9DG

        Number of registration:            3153084

        Authorised Share Capital:          1,000

        Issued Share Capital:              2
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                                   SCHEDULE 3

        1.   The Vendor has full power and authority to enter into and
             perform its obligations under this Agreement and the signing
             of this Agreement does not violate any provision of the
             Vendor's Certificate of Incorporation.

        2.   The Vendor is a company duly incorporated under the laws of
             the State of Delaware, USA.

        3.   The execution of this Agreement, nor the consummation of the
             transaction herein contemplated, nor the fulfillment of or
             compliance with the terms and provisions hereof will breach
             any current provisions of English law nor 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 Vendor is a party or by
             which it is bound.
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        SID INSTRUMENTS INC.



        By:  Earl R. Lewis
           -------------------
             Earl R. Lewis
             President

        ATI ACQUISITION CORP.



        By:  Robert J. Rosenthal
           ------------------------
             Robert J. Rosenthal
             Vice President

        THERMO INSTRUMENT SYSTEMS INC.



        By:  Earl R. Lewis
             -----------------
             Earl R. Lewis
             Executive Vice President