Exhibit 10.8


        The Directors
        Thermo Electron
        Corporation 
        81 Wyman Street 
        Waltham M.A. 02254
        U.S.A.



                                                               July 1995

        Dear Sirs

        We are pleased to advise you that Barclays Bank PLC (the  "Bank")
        has agreed to provide in aggregate short term facilities of up to
        US$100,000,000 (one hundred million United States ("US") Dollars)
        or its currency  equivalent (referred  to as  the "Facility")  to
        Thermo  Electron   Corporation   (the   "Parent")   and   certain
        Subsidiaries as may be nominated from time to time in  accordance
        with clause 3 (such companies being individually referred to as a
        "Borrower", collectively the "Borrowers") as detailed below.

        This Facility Letter cancels and replaces the existing
        US$55,000,000 facility provided by the Bank
        to the Parent and its Subsidiaries.

        The Schedules attached hereto form part of the terms and
        conditions of this letter.

        The Facility will be available for utilisation by the Borrowers,
        subject to the following terms and
        conditions:-

        1.  Options Available Within and Utilisation of the Facility
            --------------------------------------------------------

           The Facility may be utilised by way of  the following options
           and in  accordance  with  the  provisions  of  the  Schedules
           related thereto.-

           Sterling Money Market Loan (see Schedule A) and/or
           Sterling Overdraft (see Schedule B) and/or
           Currency Money Market Loan (the "Currency MML") (see Schedule
           C) and/or
           Foreign Currency Overdraft (see Schedule D) and/or
           Revolving Acceptance Credit (the "Credit") (see Schedule E)
           and/or
           Bonds Guarantees and Indemnities (see Schedule F) and/or
           Letters of Credit (see Schedule G) and/or
           Ancillary Facilities (see Schedule H).
PAGE

           Within the Facility the aggregate of the liabilities due,
           owing or incurred thereunder shall not
           at any time exceed US$100,000,000 (or its currency
           equivalent).

           The US dollar equivalent of the currency or currencies
           utilised or available to be utilised under the Facility may
           be calculated by the Bank at any time by reference to the
           Bank's spot rate of exchange in the London Foreign Exchange
           Market for the sale of the relevant currency or currencies
           for US dollars.

           Allocations under  the Facility  that are  made available  to
           Borrowers or the Parent by branches or affiliates of the Bank
           in countries outside of  the United Kingdom will  be governed
           by the terms of the Facility as detailed herein, except where
           specifically superceded by local arrangements.

        2. Availability
           ------------

        2.1 This offer is  available to the  Parent for acceptance  until
            one Month from the date of  this letter after which date  the
            offer will  lapse unless  extended in  writing by  the  Bank.
            Acceptance is to be signified as stated in clause 18 below.

        2.2 All monies  owing  under  the  Facility  are  repayable  upon
            written demand by  the Bank  and any undrawn  portion may  be
            cancelled by the Bank at  any time.  Following demand  and/or
            cancellation, no further  utilisation may be  made under  the
            Facility.  If  demand for  repayment is made  the Bank  shall
            have in addition the  right to call for  full cash cover  for
            the amount of contingent liabilities outstanding to the  Bank
            hereunder.

           The Parent shall indemnify the Bank on demand against any
           loss or expense which the Bank
           may reasonably sustain or incur as a direct consequence of
           making such demand.

           In the absence  of demand  or cancellation by  the Bank,  the
           Facility is available for utilisation until 12 April 1996 and
           no liability  or liabilities  incurred may  extend more  than
           three  months  beyond  the   above  mentioned  expiry   date.
           However, the Bank will  be pleased to discuss  the Borrower's
           requirements shortly before that date.

        3.   Subsidiaries as Borrowers
             -------------------------

        3.1 The Parent  may  designate  any  of  its  Subsidiaries  as  a
            Borrower under this Facility Letter  by giving not less  than
            10 days  notice thereof  to the  Bank.   No such  designation
            shall take effect until such  Subsidiary and the Parent  have
            executed a deed of accession in the form set out in  Schedule
PAGE

            1, and  the Bank  has  received and  found to  he  reasonably
            satisfactory  to   it   such  other   documents,   (including
            constitutional documents, board  minutes, necessary  licences
            or consents, and legal opinions) and information as the  Bank
            may reasonably require.  In addition, no Subsidiary which has
            acceded as a Borrower pursuant to this clause may utilise the
            Facility, or any option within the Facility until the  Parent
            has  made a request pursuant to clause 3.2 below and the Bank
            has agreed to such request.

        3.2 Following a request from the Parent in the form contained  in
            Schedule 2,  the Bank  may from  time to  time by  notice  in
            writing to  the  Parent allocate  to  any Subsidiary  of  the
            Parent (which has  acceded as a  Borrower pursuant to  Clause
            3.1 above) a tranche  of the Facility and/or  one or more  of
            the options  (detailed  in  clause 1)  contained  within  the
            Facility.  If the Bank does so, that tranche will not then be
            available to the Parent or other Borrowers, and the  Facility
            available to them will reduce accordingly.

        3.3 Each Borrower, by  its execution  of the  deed of  accession,
            irrevocably appoints the Parent as its agent for all purposes
            of or connected with this Agreement.  The Bank may rely  upon
            any document signed by  or on behalf of  the Parent as if  it
            had been signed by each and every other Borrower.  The Parent
            may give a good receipt for any sum payable to each and every
            other Borrower hereunder.

        4.  Interest/Fees/Charges
            ---------------------

           The interest  and/or fees,  and/or  charges payable  on  each
           option within the Facility will be calculated and  be payable
           in accordance with the relevant schedule to this Agreement.

        5 .     Interest on an Overdue Amount
                -----------------------------

        5.1If any moneys payable under this Facility are not paid when
           due by the Borrowers or the
           Parent:

           (i) interest will  be charged  on the  overdue amounts,  on a
               daily basis,  from the  due date  to the  date of  actual
               payment;

           (ii)   the amount  of such  interest  shall be  calculated  by
               reference to successive  interest periods,  (the duration
               of such interest periods shall be selected by the Bank at
               its discretion).

        5.2Interest shall be charged at the rate per annum determined by
           the Bank  to  be  equal to  1%  above  the rate  which  would
           otherwise have been applicable  to such overdue amount  under
           the provisions of  the relevant Schedule  if such amount  had
           been non-overdue principal  (except that in  the case of  any
PAGE

           amount  that  does  not  have  an  applicable  interest  rate
           hereunder the rate  charged shall  be 2% per  annum over  the
           Bank's Base Rate rate current  from time to time).   Interest
           so accrued  shall be  due on  demand or  (in  the absence  of
           demand) on the  last day  of the default  interest period  in
           which it accrued and, if  unpaid, shall be compounded  on the
           last  day  of  that  and  each  successive  interest  period.
           Interest on overdue amounts  shall be charged and  compounded
           on this basis after as well as before  any judgement obtained
           hereunder.

        6.  Guarantees
            ----------

           The repayment of each  Borrower's obligations hereunder  will
           be guaranteed by the Parent  by    the execution of  a guarantee
           acceptable to the Bank in the principal sum of US$100,000,000
           plus interest and other liabilities as detailed therein.

        7.      Fees
                ----

              The Parent shall pay to the Bank the following fees:

              (i)  an arrangement fee of #65,000 upon acceptance by the
                   Parent of the Facility; and
              (ii) a facility  fee  of  #35,000  per  annum  annually  in
                   advance during the continuation of the Facility.

        8.  Cancellation
            ------------

           Any undrawn part of the amount of the Facility may be
           cancelled by the Parent in minimum amounts of US$1,000,000
           and multiples of US$500,000 subject to the Parent giving the
           Bank not less than seven days' notice in writing (such
           notice, once given, shall be irrevocable).

           Amounts which are cancelled will no longer be available for
           drawing.

        9.   Change of Circumstances
             -----------------------

           In the event of any change in applicable law or regulation or
           the existing requirements of, or any new requirements being
           imposed by, the Bank of England or other regulatory authority
           the result of which, in the sole opinion of the Bank, is to
           increase the cost to it of funding, maintaining or making
           available the Facility (or any undrawn amount thereof) or to
           reduce the effective return to the Bank then the Borrowers
           and/or, as appropriate, the Parent shall pay to the Bank,
           upon receipt of documentation evidencing such increased cost
           or reduction, as the case may be, such sum as may be
           certified by the Bank to the Borrowers and/or the Parent as
           shall compensate the Bank for such increased cost or such
           reduction.
PAGE

        10. Set-off
            -------

           Any sum of  money at  any time  standing to the  credit of  a
           Borrower or the Parent with the Bank in any currency upon any
           account or otherwise (whether or not any such account is held
           in such Borrower's or the  Parent's name) or provided  to the
           Bank as  cash  cover for  any  bills and/or  any  outstanding
           liabilities under the Facility, may be applied by the Bank at
           any time  (upon  5  Business  Days  written  notice  to  such
           Borrower and the Parent) in  or towards the discharge  of any
           money or liabilities now or hereafter due, owing  or incurred
           to the Bank by such Borrower or the Parent hereunder (whether
           as principal or surety).

        11. Indemnity
            ---------

        11.1 The Parent  shall  indemnify  the Bank  on  demand  (without
           prejudice to the Bank's  other rights) for any  expense, loss
           or liability reasonably incurred  by the Bank in  consequence
           of (i) any default or delay by the Borrowers or the Parent in
           the payment of any amount when due under this letter, or (ii)
           all or  part  of  the  Facility  being  prepaid  or  becoming
           repayable otherwise than on the maturity of the  then current
           interest  period  including,  without  limitation   any  loss
           (including loss of margin), expense or liability sustained or
           incurred by  the Bank  in any  such event  in liquidating  or
           re-deploying  funds  acquired  or  committed  to  fund,  make
           available or maintain the Facility (or any part of it).

        11.2 If, for any reason, any amount payable under this letter  is
           received or recovered  in a  currency (the "other  currency")
           other than that in which it is required to  be paid hereunder
           (the "contractual  currency"), then  to the  extent that  the
           payment to  the  Bank  (when  converted  to  the  contractual
           currency at the then applicable rate of exchange) falls short
           of the amount so payable under this letter, the Parent shall,
           as a separate and independent obligation, fully indemnify the
           Bank against the amount of the shortfall.  For the purpose of
           this sub-clause the expression  "rate of exchange" means  the
           rate at which the Bank  is able as soon as  practicable after
           receipt to purchase the  contractual currency in London  with
           the other currency.

        12. Illegality
            ----------

            If, at any  time, the  Bank determines that  it is,  or will
            become unlawful or contrary to any  directives of any agency
            or any country  or state for  it to  make, fund or  allow to
            remain outstanding all or part of the Facility, and/or carry
            out  all  or  any  of  its  other  obligations  towards  the
            Borrowers and the  Parent under  this letter, then  upon the
            Bank notifying the Parent  of such event, within  30 days of
            that notification or such earlier date  (if any) as the Bank
PAGE

            shall certify to  be necessary  to comply with  the relevant
            law or  directive,  the  Borrowers  and/or  the  Parent  (as
            appropriate) shall prepay any  principal amounts outstanding
            together with any accrued interest thereon.

        13. Representations and Warranties
            ------------------------------

        13.1 By accepting this letter the Parent and each Borrower
             represents and warrants that:

            (a) Statutes:  The   Parent   and  each   of   its  Material
                ---------
                Subsidiaries are  duly  organised,  existing  and (where
                relevant)  in  good  standing  under  the  laws  of  the
                jurisdictions of their respective incorporation and have
                the  corporate   power  and   authority  to   own  their
                respective property  and  assets  and  to  transact  the
                businesses in  which  they respectively  are  engaged or
                presently propose to engage  and are duly  qualified and
                (where  relevant)   in   good   standing   as   foreign
                corporations.

            (b) Corporate Power and Authority: Borrowers: Each of the
                -----------------------------------------
                Borrowers has the corporate power, and has taken all
                necessary corporate action (including, without
                limitation, any consent of stockholders required by law
                or by its constitutional documents) to authorise it to
                execute, deliver and perform the terms and provisions of
                and to incur its obligations under this Agreement and to
                borrow hereunder or otherwise utilise the Facility. This
                Agreement has been or, when executed, will be duly
                authorised, executed and delivered by each Borrower and
                constitutes the legal, valid and binding obligation of
                that Borrower enforceable in accordance with its terms
                (except as the enforceability thereof may be limited by
                insolvency or similar laws of general application
                affecting creditors' rights and by general principles of
                equity).

            (c) Corporate Power and Authority: Guarantor: The Parent as
                -----------------------------------------
                Guarantor has the corporate power and has taken all
                necessary corporate action (including, without
                limitation, any consent of stockholders required by law
                or by its constitutional documents) to authorise it to
                execute deliver and perform the terms and provisions of
                and to incur its obligations under the Guarantee.  The
                Guarantee has been duly authorised executed and
                delivered by the Parent thereto and will when executed
                constitute the legal valid and binding obligation of the
                Parent enforceable in accordance with its terms (except
                as the enforceability thereof may be limited by
                insolvency or similar laws of general application
                affecting creditors' rights and by general principles of
                equity).
PAGE

            (d) Compliance with  other Instruments:  Neither  the Parent
                ----------------------------------
                nor any  Material  Subsidiary is  in  default  under any
                material agreement  to  which  it is  a  party,  and the
                execution, delivery and performance by each Borrower and
                the Parent, as  the case may  be, of  this Agreement and
                the Guarantee (a)  will not contravene  any provision of
                Applicable  Law,  (b)  will  not  conflict  with  or  be
                inconsistent with or result in any  breach of any of the
                terms,  covenants,  conditions  or   provisions  of,  or
                constitute a default under, or result in the creation or
                imposition of any Encumbrance on  any of the property or
                assets of the Parent or any Material Subsidiary pursuant
                to the terms of any  indenture, mortgage, deed to secure
                debt, deed  of  trust, or  other  material  agreement or
                instrument  to   which  the   Parent  or   any  Material
                Subsidiary is a signatory or by  which it is bound or to
                which it  may  be  subject,  (c)  will  not  violate any
                provision of the constitutional  documents of the Parent
                or any corporate  Material Subsidiary  and (d)  will not
                require any Governmental Approval.

            (e) Financial  Statements   of   Group:   The   consolidated
                -----------------------------------
                financial statements of the  Parent and its Subsidiaries
                dated 1st  January  1994  and  the  related consolidated
                statements of income  (including the notes thereto), are
                all true  and  correct  in  all  material  respects  and
                present fairly the  consolidated financial  condition of
                the Parent  and its  Subsidiaries at  that date  and the
                results of their  operations for  the year  then ending.
                To the  Parent's knowledge  neither  the Parent  nor any
                Material Subsidiary had as at  such date any significant
                liabilities, material to the Parent and its subsidiaries
                on  a  consolidated   basis,  contingent   or  otherwise
                (including liabilities for Taxes  or any unusual forward
                or long-term commitments) which were not disclosed by or
                reserved against in the financial statements referred to
                above or in the notes thereto, and there are no material
                unrealised or anticipated  losses from  any unfavourable
                commitments  of   the  Parent.     All   such  financial
                statements were  prepared in  accordance  with generally
                accepted accounting principles  applied on  a consistent
                basis  throughout  the  periods  involved.    Since  1st
                January 1994 there  has been no  material adverse change
                in the operations,  business, property or  assets of, or
                in the condition  (financial or  otherwise) or prospects
                of, the Parent and its Material Subsidiaries, taken as a
                whole.

            (f) Governmental  Approvals:  No  Governmental  Approval  is
                ------------------------
                required to authorise, or is required in connection with
                the  execution,   delivery  and   performance   of  this
                Agreement or the Guarantee.

            (g) Title to Properties:  Each of the Parent and its Material
                --------------------
PAGE

                Subsidiaries has good and marketable  title to its owned
                properties,  including   the   properties   and   assets
                reflected in  the  financial statements  referred  to in
                paragraph (f)  above.    None  of  those  properties  is
                subject to  any  Encumbrance except  as  referred  to in
                those financial  statements and  possible  title defects
                and Encumbrances which do  not materially interfere with
                the use  or materially  detract from  the value  of such
                properties or  the  operations  of  the  Parent  or  the
                relevant Material Subsidiary.

            (h) Taxes :  Each of the Parent  and its Material Subsidiaries
                -----
                has filed  or  caused  to  be  filed  all  declarations,
                reports and tax  returns including,  in the  case of the
                Parent and  each  Material  Subsidiary  located  in  the
                United States, all federal and  state income tax returns
                which it is  required by law  to file, and  has paid all
                Taxes which are shown  as being due  and payable on such
                returns or on any assessments made  against it or any of
                its properties.  The accruals  and reserves on the books
                of the Parent  and its Material  Subsidiaries in respect
                of Taxes  are adequate  for  all periods.    Neither the
                Parent nor any Material Subsidiary  has any knowledge of
                any unpaid  adjustment, assessment  or any  penalties or
                interest of significance, or any  basis therefor, by any
                taxing authority  for  any  period,  except  those being
                contested in good  faith and  by appropriate proceedings
                which  effectively   stay   the   enforcement   of   any
                Encumbrance and the attachment of a penalty.

            (i) Solvency: The Parent (i) acknowledges that it will have
                ---------
                received, before the execution of its Guarantee, fair
                consideration and reasonably equivalent value for the
                obligations incurred or to be incurred by it thereunder,
                (ii) represents and warrants that after giving effect to
                such obligations (1) the present fair saleable value of
                the assets of it exceeds its liabilities in that it
                retains sufficient capital reasonably to anticipate the
                needs and risks of its ongoing business, and (2) it has
                not incurred (actually or contingently) debts beyond its
                ability to pay such debts as they mature, and that the
                present fair saleable value of its assets is greater
                than that needed to pay its probable existing debts as
                they become due.

            (j) Disclosure:   Neither  this  Agreement,  nor  any  other
                ----------
                document, certificate or statement furnished to the Bank
                by or  on behalf  of either  Borrower  or the  Parent in
                connection herewith contains  any untrue  statement of a
                material  fact  or  omits  to   state  a  material  fact
                necessary in  order  to  make  the  statements contained
                herein and  therein not  misleading.   There is  no fact
                peculiar  to  the   Parent  or   any  of   its  Material
                Subsidiaries which materially  adversely affects  or may
PAGE

                (as far  as  the  Parent  can  now  foresee)  materially
                adversely affect  the business,  property or  assets, or
                financial condition  of  the  Parent  and  its  Material
                Subsidiaries taken as a whole which has not been set out
                in  this   Agreement,   or  in   the   other  documents,
                certificates and statements furnished to  the Bank by or
                on behalf of  the Parent,  prior to  the date  hereof in
                connection with  the transactions  contemplated  by this
                letter.

        13.2Each party providing the same shall  be deemed to repeat the
            representations and  warranties contained  in  the preceding
            sub-clause  on  each   occasion  on   which  there   is  any
            utilisation  of   the   Facility   by   reference   to   the
            circumstances then existing.

        14. Positive Covenants
            ------------------

        14.1 Use of Proceeds
             ---------------

           Each Borrower undertakes  that the  proceeds of the  Facility
           will be used for the general working capital  purposes of the
           Borrowers.  None of such  proceeds shall be used  to purchase
           or carry,  or to  reduce or  retire or  refinance any  credit
           incurred to purchase or  carry, any margin stock  (within the
           meaning of Regulations U and X) or to extend credit to others
           for the purpose  of purchasing  or carrying  any such  margin
           stock.  If  requested by  the Bank, the  Parent will  deliver
           statements in  conformity with  the  requirements of  Federal
           Reserve Form U-l referred to in Regulation U.

        14.2 Financial Information for Group
             -------------------------------

             The Parent will deliver to the Bank:

             (a) within 90 days after the end of each year of the  Parent
                 and its  Subsidiaries  an audited  consolidated  balance
                 sheet of the      Parent as at  the end  of such  year, and
                 audited consolidated statements of income and cash  flow
                 of the Parent and its Subsidiaries for such year, all in
                 reasonable detail and  with the  unqualified opinion  of
                 Arthur Andersen (or  other independent certified  public
                 accountants  of  recognised  standing  selected  by  the
                 Parent and reasonably satisfactory to the Bank) together
                 with the management letter  prepared in connection  with
                 such audited  financial  statements, provided  that  the
                 Parent may make a change in its accounting principles in
                 any year,  so long  as (w)  such change  or changes  are
                 clearly reflected in  the annual audit  report, and  (x)
                 any principle has  been concurred in  by the Parent  and
                 the Parent's  independent certified  public  accountants
                 and is in accordance with generally accepted  accounting
                 principles;
PAGE

            (b) copies of its quarterly results on Form 10-Q and its
                audited Consolidated Profit and Loss Account and Balance
                Sheet (in the form of an Annual Report and/or form 10-K,
                as appropriate) not later than 45 days from the end of
                each quarter and 90 days from the end of each accounting
                reference period respectively; and

            (c) with reasonable  promptness,  such  further  information
                regarding the business  affairs and financial  condition
                of the Parent or any Material Subsidiary as the Bank may
                reasonably request.

        14.3 Maintenance of Books: Inspection of Property and Records
             --------------------------------------------------------

             The Parent shall and shall procure that each of its Material
             Subsidiaries shall prepare or cause to be prepared (a) its
             annual statements and reports in accordance with generally
             accepted accounting principles and permit any person
             designated by the Bank to visit and inspect any of its
             properties, corporate books and financial records, and to
             discuss its accounts, affairs and finance with the principal
             officers of the Parent and such Material Subsidiary during
             reasonable business hours, and upon reasonable prior notice,
             from time to time, as the Bank may reasonably request and
             (b) its interim statements and reports in accordance with
             methods historically used by such Material Subsidiary, as
             the case may be, as such methods have yielded financial
             information which has historically not required material
             annual adjustments to bring such information into compliance
             with generally accepted accounting principles.

        14.4 Maintenance of Properties
             -------------------------

             The Parent shall and shall procure that each of its Material
             Subsidiaries shall maintain, preserve, protect and keep,  or
             cause to be maintained,  preserved, protected and kept,  its
             properties and every  part thereof in  good repair,  working
             order and  condition, and  from time  to time  will make  or
             cause to be made all  needful and proper repairs,  renewals,
             replacements,  extensions,   additions,   betterments,   and
             improvements thereto,  so    that the  business carried  on in
             connection therewith  may  be  properly  and  advantageously
             conducted at  all times  Provided that  the Parent  and  its
             Material Subsidiaries  shall not  be  obliged to  repair  or
             replace any such  properties which have  become obsolete  or
             unsuitable or inadequate for the purpose for which they  are
             used.

        14.5 Maintenance of Insurance
             ------------------------

             The Parent shall and shall procure that each of its Material
             Subsidiaries   shall   maintain   liability   and   worker's
             compensation insurance  (or maintain  a legally  sufficient,
             fully funded, programme  of self-insurance against  worker's
PAGE

             compensation  liabilities),   adequate  insurance   on   its
             properties against such hazards and in at least such amounts
             as is customary in the business  and, at the request of  the
             Bank,  the  Parent  will  forthwith  deliver  an   officer's
             certificate specifying the details of the insurance then  in
             effect.

        14.6 Taxes
             -----

             The Parent shall and shall procure that each of its Material
             Subsidiaries shall pay and discharge all Taxes prior to  the
             date on which         penalties attach thereto,  and will  pay all
             Taxes which, if unpaid, might become an Encumbrance upon any
             of its property  Provided that the  Parent and its  Material
             Subsidiaries shall not be required to pay and discharge  any
             such Tax so long as the legality or amount thereof shall  be
             promptly  contested  in  good   faith  and  by   appropriate
             proceedings which effectively  stay the  enforcement of  any
             Encumbrance and the attachment of  a penalty and the  Parent
             or such Material Subsidiary, as the case may be, shall  have
             set aside appropriate reserves  therefor in accordance  with
             generally accepted accounting principles.

        14.7 Existence and Status
             --------------------

             The Parent and each of its Material Subsidiaries which is  a
             corporation  shall  maintain  its  corporate  existence  and
             (where relevant) good standing in its state of incorporation
             and its qualification and (where relevant) good standing  as
             a  foreign  corporation  in  all  jurisdictions  where   its
             ownership of property or its business activities cause  such
             qualification to be required.

        14.8 Litigation
             ----------

             The Parent  shall give  prompt  notice to  the Bank  of  any
             material pending  legal proceedings.   For  the purposes  of
             this Clause 14.8, only pending legal proceedings which would
             be required to be reported by the Parent for Securities  and
             Exchange Commission Filings need be reported to the Bank.

        14.9 Stockholder Reports, etc
             ------------------------

             Promptly after  the  same  are available,  the  Parent  will
             provide to the Bank copies of all publicly available current
             reports on Form 8-K, proxy statements and prospectuses filed
             with  the  Securities  and  Exchange  Commission  under  the
             Securities Act 1933, as  amended or the Securities  Exchange
             Act  1934  as  amended,  as  the  case  may  be,  (excluding
             prospectuses relating to  employee stock  option or  benefit
             plans).

        15.  Payments and Gross-Up
             ---------------------
PAGE


        15. I     All payments  by  a  Borrower,  whether  of  principal,
             interest or otherwise, shall be  made to the Bank not  later
             than 12 noon (London time) on the due date in same day funds
             (or as  otherwise expressly  agreed  by the  Bank),  without
             set-off  or  counterclaim  and  free  of  any  deduction  or
             withholding whatsoever, including  without prejudice to  the
             generality of  the foregoing,  for or  on account  of  Taxes
             unless that Borrower  is required  by law to  make any  such
             payments subject to deduction  or withholding on account  of
             Taxes, in which  case the  sum payable by  that Borrower  in
             respect of which such  deduction or withholding is  required
             to be made  shall be  increased to the  extent necessary  to
             ensure  that,  after  the   making  of  such  deduction   or
             withholding, the Bank  receives and retains  (free from  any
             liability in respect of any such deduction or withholding) a
             net sum equal to the sum which it would have received and so
             retained had no such deduction  or withholding been made  or
             required to be made.

        15.2 Without prejudice to the provisions  of Clause I5.1, if  the
             Bank is required by  law to make any  payment on account  of
             Taxes (other  than  Taxes  on its  overall  net  income)  or
             otherwise  on  or  in  relation  to  any  sum  received   or
             receivable by  the  Bank  hereunder,  or  any  liability  in
             respect of any such payment  is imposed, levied or  assessed
             against the Bank, the relevant Borrower shall, on demand  by
             the  Bank,  indemnify  the  Bank  against  such  payment  or
             liability together with any interest penalties and  expenses
             payable or incurred in  connection therewith (except to  the
             extent that  such interest  penalties and  expenses  results
             from the late settlement of such payment or liability by the
             Bank).

        15.3 If the Bank intends to make a claim pursuant to clause 15.2,
             it shall notify the relevant Borrower of the event by reason
             of which  it  is entitled  to  do  so and  provide  to  that
             Borrower in reasonable  detail a calculation  of the  amount
             claimed Provided that nothing herein shall require the  Bank
             to disclose any information relating to the organisation  of
             its affairs  which  the Bank  shall,  in its  sole  opinion,
             consider to be confidential.

        16.  Interpretation
             --------------

        16.1 In this Facility Letter, unless the context otherwise
             requires: -

             "Agreement" means the agreement arising on the Borrowers'
             acceptance of the offer contained in this Facility Letter;

             " Applicable Law"  means (i)  all applicable  common law  and
             principles of equity and  (ii) all applicable provisions  of
             all (a)  constitutions,  statutes,  rules,  regulations  and
             orders of  governmental bodies,  (b) Governmental  Approvals
PAGE

             and (c)  orders, decisions,  judgments  and decrees  of  all
             courts and arbitrators;

             "Base Rate" means the Bank's base rate published from time
             to time;

             " Business Day"  means  a day on which the relevant London
             financial markets  are  open for  dealings  in  eurocurrency
             deposits  between  banks  and,   if  a  payment  falls   due
             hereunder, also,  a  day  on which  banks  in  the  relevant
             principal financial centre (as  determined by the Bank)  for
             the  relevant  currency  are  open  for  dealings  in   such
             currency.  Should any requirement under this letter fall due
             on a date which is not  a Business Day then such date  shall
             be extended to the next Business Day;

             "Code" means the Internal Revenue Code of 1986, as amended
             from time to time, and the
             regulations promulgated and the rulings issued thereunder;

             "  Encumbrance" includes  any   mortgage,  pledge, security
             interest,  encumbrance,  lien  or  charge  of  any  kind  or
             description (and  shall  include,  without  limitation,  any
             agreement to give any of the foregoing, any conditional sale
             or other title retention agreement, any lease in the  nature
             thereof including any  lease or similar  arrangement with  a
             public authority executed in connection with the issuance of
             industrial development  revenue bonds  or pollution  control
             revenue bonds, and the  filing of or  agreement to give  any
             financing statement under the Uniform Commercial Code of any
             jurisdiction);

             "Governmental Approval" means any order, permission,
             authorization, consent, approval, licence, franchise, permit
             or validation of, exemption by, registration or filing with,
             or report or notice to, any governmental agency or unit, or
             any public commission, boarder authority;

             "Guarantor" means the Parent;

             " Guarantee" means the guarantee executed  and delivered  to
             the Bank pursuant to Clause 6;

             " Material Subsidiary" means  any Subsidiary  of the  Parent
             designated as a Borrower pursuant to Clause 3 and any  other
             Subsidiary of the Parent which  alone, or together with  its
             own subsidiaries, represents either or both of (a) not  less
             than 5 % of the net earnings before Taxes of the Parent  and
             its Subsidiaries taken as a whole in the fiscal year of  the
             Parent most recently ended  or (b) not less  than 5% of  the
             consolidated book value of the assets of the Parent and  its
             subsidiaries taken as  a whole  as of  the last  day of  the
             fiscal year of the Parent most recently ended, and "Material
             Subsidiaries" shall be construed accordingly;
PAGE

             "Month" means a  period starting  on one day  in a  calendar
             Month and  ending  on  the corresponding  day  in  the  next
             calendar Month or,  if that is  not a Business  Day, on  the
             next Business  Day unless  that  falls in  another  calendar
             Month in which case it  shall end on the preceding  Business
             Day, save that where  a period starts  on the last  Business
             Day in a Month or there is no corresponding day in the Month
             in which the period ends, that period shall end on the  last
             Business Day in the later Month;

             "Outstanding Amount" means, in relation to a Bank Guarantee
             at any time, the maximum
             actual and contingent liability of the Bank under that Bank
             Guarantee at that time;

             "Regulation U or X" shall mean Regulation U or X
             respectively of the Board of Governors of the Federal
             Reserve System, as in effect from time to time, and any
             regulation successor thereto;

             "Sterling" and "#" means lawful currency of the United
             Kingdom;

             "Subsidiary" shall mean a subsidiary undertaking within the
             meaning of Section 736 of the
             Companies Act 1985;

             " Tax"  shall mean, with respect to any person or entity,  any
             federal, state or foreign  tax, assessment, customs  duties,
             or other governmental charge, levy or assessment  (including
             any withholding tax) upon such person or entity or upon such
             person's or  entity's assets,  revenues, income  or  profits
             (other than  United Kingdom  income taxes  imposed upon  the
             Bank);

             "U.S. Dollar", "Dollar" and "I" shall mean lawful money of
             the United States of America.

        16.2 Reference to any statutory provision includes any amended or
             re-enacted version of  such provision with  effect from  the
             date on which it comes into force.

        16.3 Save as otherwise expressly  provided herein, references  in
             this Agreement  to  this  Agreement or  any  other  document
             include reference to this  Agreement or such other  document
             as varied, supplemented  and/or replaced  as agreed  between
             the parties hereto or  as permitted hereby  or to which  the
             Bank shall have consented from time to time.

        16.4 References to  Clauses, sub-clauses,  paragraphs,  Schedules
             and annexures are to be construed as references to  Clauses,
             sub-clauses, paragraphs,  Schedules  and annexures  of  this
             Agreement unless otherwise stated.
PAGE


        16.5 Clause headings are for convenience only and shall not
             affect the construction hereof.

        17.  Governing Law and Jurisdiction
             ------------------------------

        17.1 This Facility Letter shall be governed by and construed in
             accordance with English law.

        17.2 The Parent  and its  Material  Subsidiaries agree  that  any
             legal action or proceedings arising out of or in  connection
             with this Facility Letter may  be brought in the High  Court
             of  Justice  in  England  and  irrevocably  submit  to   the
             jurisdiction of that Court, provided that this submission to
             jurisdiction shall not (and shall not be construed so as to)
             limit the  Bank's  right  to take  proceedings  in  whatever
             jurisdiction shall seem fit to the Bank,

        18.  Acceptance
             ----------

             Prior to the Facility being utilised, the Parent shall
             provide the Bank with the following:-

            (a) the enclosed duplicate of this letter duly signed on each
                Borrower's  and  the  Parent's  behalf  as  evidence   of
                acceptance of the terms and conditions stated herein;

            (b) a certified true copy of a resolution of the Parent's
                Board of Directors: -

               (i) accepting the Facility on the terms and conditions
                   stated herein,

               (ii)    authorising a  specified  person, or  persons,  to
                   sign and return  to the  Bank the  duplicate of  this
                   letter, and

               (iii)   authorising the  Bank to  accept instructions  and
                   confirmation in connection  with the Facility  signed
                   in accordance with the Bank's signing mandate current
                   from time  to time,  and  to accept  instructions  in
                   connection  with  drawings  under  the  Facility   by
                   telephone from any person specifically authorised  to
                   give such telephone instructions,

            (c) confirmed specimens of the signatures of those officers
                referred to in (b)(ii) above; and

            (d) the Guarantee referred to  in clause 6  duly executed by
                the Parent and in the form required by the Bank; and

            (e) an opinion of the legal  counsel to the Parent addressed
                to the  Bank in  a form  reasonably satisfactory  to the
                Bank and  which opinion  includes confirmation  that the
PAGE

                Parent is legally empowered to accept and enter into the
                terms and  conditions  of this  letter  and  the related
                guarantee.

        Yours faithfully
        For and on behalf of
        Barclays Bank PLC






        /s/ Jonathan L Gray


        Jonathan L Gray
        Relationship Director - North America
        Large Corporate Banking




        Accepted on the terms and conditions stated herein.

        For and on behalf of

        THERMO ELECTRON CORPORATION

             /s/ Jonathan W. Painter

        by..............................................................

        ........


        date.................10/2/95....................................

        ..............
PAGE



                                   SCHEDULE 1
                                   ----------

                            FORM OF DEED OF ACCESSION
                            -------------------------

        THIS DEED is made on          19

        BETWEEN

        (1)            [              ] ("the Borrower");

        (2)    THERMO ELECTRON CORPORATION ("the Parent") on behalf of
               itself and each of the other Borrowers (as defined in the
               Facilities Letter); and

        (3)    BARCLAYS BANK PLC ("the Bank").

        WHEREAS this Deed is supplemental to the facilities letter dated
        [         ], 1995 and made
        between the Parent and the Bank ("the Facilities Letter").

        NOW THIS DEED WITNESSETH:-

        1.     Accession of Borrower
               ---------------------

               In consideration  of the  Bank  agreeing to  the  Borrower
               becoming an additional  Borrower pursuant to  Clause 3  of
               the Facilities Letter  and by the  execution of this  Deed
               the Borrower agrees to observe  and be bound by the  terms
               and provisions of  the Facilities Letter  insofar as  they
               apply to the Borrower as if  it were an original party  to
               the Facilities Letter.

        2.     Interpretation
               --------------

               This Deed shall be read as one with the Facilities  Letter
               so  that  any  reference  therein  to  "this   Agreement",
               "hereunder" and similar expressions  shall include and  be
               deemed to include this Deed.

        3.     Conditions precedent
               --------------------

              The obligations of the Bank  hereunder are subject to  the
              condition that the Bank is satisfied that  all appropriate
              conditions precedent have been  fulfilled by the  Borrower
              pursuant to Clause 3 of the Facilities Letter.
PAGE

        IN WITNESS whereof the parties hereto have caused this Deed to be
        duly executed on the date first
        written above.

        EXECUTED AS A DEED by
        [THE BORROWER]
        in the presence of:-



        EXECUTED AS A DEED by
        THERMO ELECTRON CORPORATION
        in the presence of:-

                                   SCHEDULE 2
                                   ----------

                 Form of request for allocation of the Facility
                 ----------------------------------------------

        FROM:   Thermo Electron Corporation

        TO:        Barclays Bank PLC


        Dear Sirs,

        Facility Letter dated [       ] made between Thermo Electron
        -----------------------       ------------------------------
        Corporation (the "Parent") and
        ------------------------------
        Barclays Bank PLC (the "Bank") (the "Facility")
        -----------------------------------------------

        We refer to the above Facility Letter.  Terms and expressions
        defined in the Facility Letter shall have
        the same meaning when used in this request.

        Pursuant to clause 3.2 of the Facility Letter, we hereby make the
        following request(s) for an allocation
        of [a] tranche(s) of the Facility: -

        Name of Subsidiary            Amount of Tranche
        ------------------            -----------------
        Option(s)
        ---------
        Requested                Requested
        ---------                ---------



        We confirm that:-

        (1)    each of the  representations and  warranties contained  in
               sub-clause  13.1  of  the  Facility  Letter  is  true  and
               accurate if made on the date hereof with reference to  the
               facts and circumstances now existing;

        (2)    on the date on which  the tranche(s) requested above  will
               be utilised there will exist no breach of the terms of the
PAGE

               Facility Letter;

        (3)    the above-named Subsidiary  has executed  and provided  to
               the Bank a  deed of  accession in the  form stipulated  by
               clause 3.1 of the Facility Letter.



        Yours faithfully



        THERMO ELECTRON CORPORATION






                                   SCHEDULE A
                                   ----------

        Sterling Money Market Loan
        --------------------------

        The Sterling Money Market Loan may be drawn in one or more
        amounts, each drawing to be a minimum amount of #500,000 and
        multiples of #100,000 thereafter for periods of 30,60 or 90 days
        at the Borrower's option or other mutually agreed period but no
        drawing shall be made for an interest period with a maturity date
        of more than three months beyond the expiry date detailed in
        clause 2.2 of the letter.

        When wishing to draw under the Sterling Money Market Loan, the
        Borrower should telephone the account holding branch of the Bank
        on or shortly before the day on which funds are required stating
        the amount of the drawing, the period required and giving
        instructions for payment of the funds.  In the event these
        instructions do not stipulate that the funds must be credited to
        the Borrower's current account with the account holding Branch
        such instructions must be confirmed by letter to the account
        holding Branch at the earliest opportunity.

        The rate of interest on each drawing will include the Bank's
        margin of 0.45% per annum added to the cost of funds to the Bank
        (such cost of funds to be conclusively determined by the Bank and
        shall include any associated costs resulting from requirements of
        the Bank of England or other governmental authorities or
        agencies, whether having the force of law or otherwise, affecting
        the conduct of the Bank's business) for the period of the
        drawing.  Interest will be payable without deduction at six
        monthly intervals if appropriate and at the maturity of each
        drawing, and calculated on the basis of actual days elapsed over
        a 365 day year.

        Each drawing, together with interest thereon, will be repaid on
PAGE


        its maturity date by debit to the Borrower's current account at
        the account holding branch.













                                   SCHEDULE B
                                   ----------

        Sterling Overdraft
        ------------------

        The Sterling Overdraft will be available on the Borrower's
        current account at the Branch with interest charged at a rate of
        1% per annum over the Bank's Base Rate current from time to time.
        Interest, together with other charges will be debited to the
        Borrower's current account at the Branch quarterly in arrears in
        March, June, September and December each year or at such other
        times as may be determined by the Bank, and such interest will be
        calculated on the basis of actual days elapsed over a 365 day
        year.
PAGE


                                   SCHEDULE C
                                   ----------

        Currency Money Market Loan
        --------------------------

        This option relates to a short term loan in any currency (other
        than sterling) which is freely transferable and convertible into
        sterling and is available to the Bank in the relevant amount for
        the relevant period in the normal course of business on the
        London Inter-Bank market.  The Bank shall be sole arbitor of the
        availability of such currencies.

        The short term currency loans may be drawn in one or more
        amounts, each drawing to be a minimum amount of the currency
        equivalent of US$500,000.  Larger drawings shall be in amounts
        which are mutually agreeable and drawings shall be for periods up
        to a maximum of six months at the Borrower's option or other
        mutually agreed periods but no drawing should be made for an
        interest period with a maturity date of more than three months
        beyond the expiry date detailed in clause 2.2 of the letter.

        When drawings are to be made, the Borrower should telephone the
        account holding branch of the Bank two business days before the
        business day on which funds are required stating the amount of
        the drawing, the period required and giving instructions for
        payment of the funds.  In the event these instructions do not
        stipulate that the funds must be credited to the Borrower's
PAGE

        current account with the Branch, such instructions must be
        confirmed by letter to the Branch at the earliest opportunity.

        The interest rate on each drawing will include the Bank's margin
        of 0.45% per annum added to the cost of funds to the Bank (such
        cost of funds to be conclusively determined by the Bank) which
        will be dependent upon the conditions prevailing in the relevant
        London financial markets for the period of the drawing.  Interest
        will be payable without deduction at six monthly intervals, if
        appropriate, and at the maturity of each drawing, and calculated
        on the basis of actual days elapsed over a 360 day year.

        Each drawing, together with interest thereon, will be repaid on
        its maturity date in the currency in which such drawing is
        outstanding in immediately available freely convertible and
        transferable funds without any set-off or counterclaim and free
        of any deduction or withholding on any ground, to such bank or
        branch of the Bank as the Bank may specify.  In the event of the
        Borrower being compelled by law to make any such deduction or
        withholding, the Borrower will pay to the Bank such additional
        amount(s) as are required to ensure that the Bank receives and
        retains a net amount equal to the full amount which it would have
        received if no such deduction or withholding had been made.

        For the purposes of this letter a "business day" shall mean a day
                            ----
        on which the relevant London financial markets are open for
        dealings in eurocurrency deposits between banks and, in addition,
        so far as concerns a day on which a payment falls to be made
        hereunder, a day on which banks in the relevant principal
        financial centre (as determined by the Bank) for the relevant
        currency are open for dealings in such currency.  Should any
        requirements under this letter fall due on a date which is not a
        business day, then such date shall be extended to the next
        business day.








                                   SCHEDULE D
                                   ----------

        Foreign Currency Overdraft
        --------------------------

        The Foreign Currency overdraft will made available in any
        currency (other than sterling) as previously agreed by and
        arranged with the Bank, and which currency is freely transferable
        and available to the Bank in the normal course of business.

        The Foreign Currency Overdraft will be available on the
        Borrower's foreign currency account at the account holding branch
        with interest charged at 1% per annum over the bank's call loan
PAGE

        rate current from time to time.  Interest together with other
        charges will be debited to the Borrower's foreign currency
        account at the account holding branch quarterly in arrears in
        March, June, September and December each year or at such times as
        may be determined by the Bank, and such interest will be
        calculated on the basis of actual days elapsed over a 360 day
        year.




















                                   SCHEDULE E
                                   ----------



        Revolving Acceptance Credit
        ---------------------------

        To enable drawings to be made under the Revolving Acceptance
        Credit (the "Credit"), the Borrower should either:
PAGE

        (I)  forward bills to the Branch to be in the Branch's hands at
        least four business days before the     funds are required.
        Bills should be drawn by the Borrower on Barclays Bank PLC, Head
        Office,   54 Lombard Street, London EC3P 3AH for fixed periods of
        30,60 or 90 days except that no    period may be selected which
        would mature more than 90 days after the expiry date detailed in 
             clause 2 of this letter.  If the selected maturity date is a
        non-business day, bills should be drawn      to mature on the
        following business day.  Individual bills should be drawn in
        amounts of #50,000  and should be made to the Bank's order and
        claused "Drawn against purchases of electronic    security
        systems" or

        (ii) forward a supply of bills to the Branch drawn as in (i)
             above, except that the dates will be left blank.  The branch
             will arrange for the supply of bills to be held by the
             Bank's Global Treasury Services Office in London ("GTS"),
             and for the dates to be completed in accordance with the
             Borrower's oral instructions when drawings are required.

        When wishing to draw under the Credit, the Borrower should
        telephone the Bank's dealers at GTS on 071 696 2496 before 12.00
        noon on the day on which funds are required, stating the amount
        required and the period, and agreeing the discount rate quoted.

        The Bank will accept the bills and will, at its option, either
        (i) discount the bills itself in which case the rate of discount
        will be the then current offer rate as quoted by the Bank for
        such bills in the London Discount Market, or (ii) offer the bills
        for discount as agent on the Borrower's behalf in the London
        Discount Market at the discount rate prevailing in such market at
        the time when discount is effected.  The proceeds after discount
        and acceptance commission will be credited to the Borrower's
        current account at the Branch.

        Acceptance commission payable at the time of acceptance will be
        charged at the rate of 0.5% per annum on the face value of each
        draft presented and will be deducted from the proceeds after
        discount.

        The Bank will debit the Borrower's current account with the face
        value of each draft upon its maturity date.  The Credit is
        revolving, however, and it will be open to the Borrower within
        the validity and terms of the Facility to present further bills
        in accordance with this clause.

        By its acceptance of the Facility, the Borrower undertakes that
        during the validity of the Credit it will ensure that there are
        sufficient purchases to cover the amounts drawn during the period
        for which such bills are drawn and which are not the subject of
        other financing arrangements.  The Borrower will provide a
        certificate to this effect, signed by an official authorised to
        draw bills, if requested by the Bank in writing.
PAGE

        The acceptance of a bill shall give rise to a debt from the
        Borrower to the Bank equal to the face value of such bill, which
        debt shall be due for payment on the maturity of such bill.

                                   SCHEDULE F
                                   ----------

        Bonds, Guarantees and Indemnities
        ---------------------------------

        The Bank is prepared to consider issuing guarantees, bonds and
        indemnities on behalf of the Borrower in respect of normally
        accepted and commercial transactions, subject to prior agreement
        with the Bank and receipt of the necessary counter indemnities.
        Pricing will be as follows:

        expiry less than 1 year       :    0.500% per annum

        one to three years       :    0.625% per annum

        three to five years      :    0.750% per annum

        Other,  including guarantees 
        with non-standard wording or
        without a fixed expiry date   :    1.000% per annum
PAGE

                                   SCHEDULE G
                                   ----------

        Letters of Credit
        -----------------

        The Bank is prepared to open Documentary Letters of Credit on
        instructions from the Borrower to provide for the purchase of
        commodities as may be agreed by the bank from time to time.  All
        Documentary Letters of Credit are issued subject to the terms and
        conditions set out in the Bank's standard form for opening
        Documentary Letters of Credit and are also subject to the
        "Uniform Customs and Practice for Documentary Credits (1983
        Revision)", or any subsequent revision as issued by the
        International Chamber of Commerce.  Pricing will be decided on a
        case by case basis.
PAGE


                                   SCHEDULE H
                                   ----------

        ANCILLARY FACILITIES
        --------------------

        Negotiation of Sterling/Foreign Currency Cheques and Bills of
        -------------------------------------------------------------
        Exchange Payable Abroad
        -----------------------

        The Bank will purchase, with recourse, suitable foreign currency
        and sterling cheques payable abroad and/or approved foreign
        currency or sterling bills of exchange payable abroad.  The
        suitability of those cheques and bills of exchange which the Bank
        is prepared to purchase is entirely at the discretion of the
        Bank, and is subject to the Uniform Rules of the Collection of
        Commercial Paper (1978 Revision).  Pricing will be decided on a
        case by case basis.

        SFET
        ----

        The Bank is prepared to consider marking a Spot and Forward
        Exchange Transaction (SFET) Facility.

        The SFET facility covers the maximum liability of the Borrower to
        the Bank outstanding at any time under contracts of not more than
        12 months duration for the forward purchase or sale of foreign
        currency for delivery at a future date and spot purchase or
        sale-of foreign currencies, but excludes purchases or sales where
        the Bank is required irrevocably to pay away funds prior to
        receiving firm confirmation of incoming cover.

        When wishing to utilise the SFET facility the Borrower should
        telephone the account holding branch.  All payment and delivery
        instructions are to be advised to and processed by the account
        holding branch and confirmed by letter at the earliest
        opportunity.

        Bankers Automated Clearing Services Limited (BACS)
        --------------------------------------------------

        The Bank is prepared to make available a BACS facility to
        accommodate
        the Company's requirements for automated payments or receipts.

        Daylight Exposure Limit (DEL)
        -----------------------------

        The Bank is prepared to make available a DEL to cover the
        aggregate of the face value of the funds which the Bank is
        required to pay away by CHAPS prior to receiving incoming funds
        to cover these payments on the same day.

        Branch Originated BACS Facility (BOBS)
        --------------------------------------

        The Bank is prepared to make available a BOBS facility to
        accommodate the Company's requirements for automated payments or
        receipts when originated by the account holding branch.
PAGE

        The Directors
        Thermo Electron Corporation
        81 Wyman Street
        Waltham,
        M.A. 02254-9046
        U.S.A.
                                                     25th July 1997

        Dear Sirs

        We refer to the letter (the _Letter_) dated July 1995 and
        subsequently varied by the letters dated 10th April 1996
        and 1st July 1996 from Barclays Bank PLC (the _Bank_)
        setting out the terms and conditions of a $100,000,000 (one
        hundred million United States Dollars) or currency
        equivalent aggregate short term facilities (the _Facility_)
        provided to Thermo Electron Corporation (the _Borrower_).

        We are pleased to vary the terms and conditions of the
        Facility Letter as follows:-

        1. Availability : In the absence of demand or cancellation
           by the Bank the Facility is available for utilisation
           until 24th July 1998 and no liability or liabilities
           incurred may extend more than three months beyond the
           above mentioned expiry date.

        2. Amount : the amount of the Facility is hereby amended to
           $150,000,000 (one hundred and fifty million United States
           Dollars).

        3. Fees : The Borrower shall pay to the Bank the following
           fees :

        i) an arrangement fee of #150,000 upon acceptance of this
           letter ; and

        ii)  a fee calculated at the rate of 0.10 per cent per
           annum payable quarterly in 
              arrears on the total amounts utilised under the
           Facility, during the continuation of 
              the Facility. 

        4. Set-Off : we hereby amend clause 10, line 4, by deleting
           the words _(upon 5 Business Days written notice to such
           Borrower and the Parent)_.

        5. Schedule A - Sterling Money Market Loan : The Bank's
           margin is hereby amended to 0.40% per annum.

        6. Schedule C - Currency Money Market Loan : The Bank's
           margin is hereby amended to 0.40% per annum.
PAGE







        7. Schedule F - Bonds, Guarantees and Indemnities :
           Commission at a rate of 0.45% per annum will be charged
           regardless of expiry, subject to a minimum of #100.

        All other terms and conditions will remain unchanged.

        Acceptance of the amended terms and conditions shall be
        signified by the Borrower returning to the Bank :-

        a) the enclosed duplicate of this letter duly signed on the
           Borrower's behalf as evidence of acceptance of the
           amended terms and conditions stated herein, and

        b) a certified true copy of a resolution of the Borrower's
           Board of Directors:-

             i)  accepting the amended terms and conditions stated
        herein, and

             ii) authorising a specified person, or persons, to
        endorse and return to the 
                 Bank the duplicate of this letter.


        Yours faithfully,
        for and on behalf of
        BARCLAYS BANK PLC




        /s/ Jonathan L Gray


        Jonathan L Gray
        Relationship Director - North America
        Large Corporate Banking

        Accepted as of the above date on the terms and conditions
        stated herein, pursuant to a resolution of the Board of
        Directors (a certified true copy of which is attached
        hereto).



        for and on behalf of
        Thermo Electron Corporation 





        /s/ Kenneth J. Apicerno
            Assistant Treasurer