EXHIBIT 1.1
                                 $250,000,000

                        THERMO INSTRUMENT SYSTEMS INC.
                          THERMO ELECTRON CORPORATION

                            UNDERWRITING AGREEMENT
                            ----------------------
                                        

                                                           January 15, 1998
Lehman Brothers Inc.
Three World Financial Center
New York, New York 10285

Goldman, Sachs & Co.
85 Broad Street
New York, New York 10004

Smith Barney Inc.
Seven World Trade Center
New York, New York 10048

Dear Sirs:

     Thermo Instrument Systems Inc., a Delaware corporation (the
"Company"), proposes to issue and sell up to $250,000,000 of a combination of
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the Company's (i) debt securities, consisting of debentures, notes or other
unsecured evidences of indebtedness which may be either senior debt securities
(the "Senior Debt Securities") or subordinated debt securities (the
"Subordinated Debt Securities"), and (ii) shares of common stock, $.10 par value
(the "Common Stock"), in one or more offerings on terms and conditions
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determined at the time of sale.  Debt Securities that may be issued by the
Company will be guaranteed (the "Guarantees"), on either a senior or
                                 ----------                         
subordinated basis, by Thermo Electron Corporation, a Delaware corporation and
the corporate parent of the Company ("Thermo Electron").  The Debt Securities,
                                      ---------------                         
the Common Stock and the Guarantees are sometimes referred to herein as the
                                                                           
"Offered Securities."  The Senior Debt Securities will be issued pursuant to an
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indenture (the "Senior Indenture") among the Company, Thermo Electron and
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Bankers Trust Company, as trustee (the "Trustee") and the Subordinated Debt
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Securities will be issued pursuant to an indenture (the "Subordinated
Indenture") among the Company, Thermo Electron and the Trustee (the Senior
Indenture and Subordinated Indenture are sometimes hereinafter collectively
referred to as the "Indentures" and individually as an "Indenture").

     From time to time, the Company and Thermo Electron may enter into one
or more terms agreements in substantially the form attached hereto as Schedule I
(each a "Terms Agreement") that provide for the sale of such designated Offered
         ---------------                                                       
Securities to, and the purchase and offering thereof by, either or both of you,
as applicable, and the underwriter or underwriters named 

 
                                      -2-



therein (the "Underwriters" or "you", which terms shall include the underwriter
              ------------      --- 
or underwriters named therein whether acting alone in the sale of Offered
Securities or as members of an underwriting syndicate), and the provisions set
forth herein (except for provisions which relate to securities other than
Offered Securities designated in the applicable Terms Agreement) shall be
incorporated by reference in any such Terms Agreement.  The applicable Terms
Agreement, including the provisions incorporated therein by reference, is herein
referred to as "this Agreement."
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     1.   Representations, Warranties and Agreements of the Company and
          ------------------------------------------------- -----------
Thermo Electron. The Company and Thermo Electron, jointly and severally,
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represent and warrant as to the Company (and its Subsidiaries) as follows,
Thermo Electron represents and warrants as to itself (and its Subsidiaries) as
follows, and the Company and Thermo Electron, jointly and severally, agree with
each Underwriter as follows:

          (a)  A registration statement on Form S-3 (No. 333-32031 and -32031-
01), including a prospectus relating to the Offered Securities of the Company
and Thermo Electron for the registration of such securities under the United
States Securities Act of 1933, as amended (the "Securities Act"), has (i) been
                                                --------------                
prepared by the Company and Thermo Electron in material conformity with the
requirements of the Securities Act and the rules and regulations (the "Rules
                                                                       -----
and Regulations") of the United States Securities and Exchange Commission (the
    -----------                                                               
"Commission") thereunder, (ii) been filed with the Commission under the
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Securities Act and (iii) become effective under the Securities Act; and each
Indenture has been qualified under the Trust Indenture Act of 1939, as amended
(the "Trust Indenture Act").  Copies of such registration statement and any
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amendments thereto have been delivered by the Company and Thermo Electron to
you.  As used in this Agreement, "Effective Date" means the date and the time as
                                  --------------                                
of which such registration statement, or the most recent post-effective
amendment thereto, if any, was declared effective by the Commission;
                                                                    
"Registration Statement" means the registration statement in the form it became
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or becomes, as the case may be, effective (including, if the Company omitted
information from the registration statement pursuant to Rule 430A(a) or files a
term sheet pursuant to Rule 434 of the Rules and Regulations, the information
deemed to be a part of the registration statement at the time it became
effective pursuant to Rule 430A(b) or Rule 434(d) of the Rules and Regulations),
including all documents incorporated by reference or deemed to be incorporated
by reference therein and the exhibits thereto and, in the event of any amendment
thereto or the filing of any abbreviated registration statement pursuant to Rule
462(b) of the Rules and Regulations relating thereto after the effective date of
such registration statement, shall also mean (from and after the effectiveness
of such amendment or the filing of such abbreviated registration statement) such
registration statement as so amended, together with any such abbreviated
registration statement; "Base Prospectus" means the prospectus included in the
                         ---------------                                      
Registration Statement; "Preliminary Prospectus" means any preliminary form of
                         ----------------------                               
prospectus supplement specifically relating to designated Offered Securities in
the form filed with, or transmitted for filing to the Commission pursuant to
Rule 424 of the Rules and Regulations, together with any accompanying
prospectus; "Prospectus Supplement" means any prospectus supplement specifically
             ---------------------                                              
relating to designated Offered Securities in the form filed with, or transmitted
for filing to, the Commission pursuant to Rule 424 under the Securities Act;
                                                                            
"Prospectus" means the Base Prospectus together with the Prospectus Supplement
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specifically 

 
                                      -3-

relating to designated Offered Securities in the form first filed with, or
transmitted for filing to, the Commission pursuant to Rule 424 under the
Securities Act following the execution of a Terms Agreement with respect to such
Offered Securities, except that if such Base Prospectus is amended or
supplemented on or prior to the date on which such Prospectus Supplement was
first filed pursuant to Rule 424, the term "Prospectus" shall refer to the Base
Prospectus as so amended or supplemented and as supplemented by such Prospectus
Supplement; "Base Prospectus," "Prospectus," "Preliminary Prospectus" and 
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"Prospectus Supplement" shall include in each case the documents, if any, filed 
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by the Company or Thermo Electron with the Commission pursuant to the United
States Securities Exchange Act of 1934, as amended (the "Exchange Act"), and
                                                         -------- ---
incorporated by reference therein; and "supplement" and "amendment", shall be
                                        ----------       ---------
deemed to refer to and include any documents incorporated by reference pursuant
to Item 12 of Form S-3 under the Securities Act that are filed subsequent to the
date of the Base Prospectus by the Company or Thermo Electron with the
Commission pursuant to the Exchange Act. Any reference to any amendment to the
Registration Statement shall be deemed to include any annual report of the
Company or Thermo Electron, as the case may be, filed with the Commission
pursuant to Section 13(a) or 15(d) of the Exchange Act after the Effective Date
that is incorporated by reference in the Registration Statement. Any reference
herein to information "contained in," "contemplated by," "described in,"
                       --------- --    ------------ --    --------- --
"disclosed in," "included in" or "set forth in" any of the foregoing documents,
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or words of similar effect, shall be deemed to include the documents
incorporated or deemed to be incorporated by reference therein.

          (b)  The Registration Statement complies as to form in all material
respects, and the Prospectus and any further amendments or supplements to the
Registration Statement or the Prospectus will, when they become effective or are
filed with the Commission, as the case may be, comply as to form in all material
respects to the requirements of the Securities Act and the Rules and Regulations
and do not and will not, as of the applicable Effective Date (as to the
Registration Statement and any amendment thereto) and as of the applicable
filing date and applicable Closing Date (as to the Prospectus and any amendment
or supplement thereto) contain an untrue statement of a material fact or omit to
state a material fact required to be stated therein or necessary to make the
statements therein (in the case of the Prospectus, in light of the circumstances
in which they were made), not misleading; provided, however, that no
representation or warranty is made as to information contained in or omitted
from the Registration Statement or the Prospectus in reliance upon and in
conformity with written information furnished to the Company by or on behalf of
any Underwriter specifically for use in the Registration Statement or the
Prospectus.  To the extent applicable, the copies of the Registration Statement
and each other document referred to in subparagraph (a) above that have been or
will be furnished to the Underwriters have been and will be identical to the
electronically transmitted copies thereof filed with the Commission pursuant to
the Commission's Electronic Data Gathering, Analysis and Retrieval System
("EDGAR"), except to the extent permitted by Regulation S-T.
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          (c)  If the Offered Securities are Debt Securities:  Each Indenture
conforms in all material respects to the requirements of the Trust Indenture Act
and the applicable rules and regulations thereunder.

 
                                      -4-

          (d)  The documents incorporated or deemed to be incorporated by
reference in the Prospectus, when they were filed with the Commission, conformed
in all material respects with the requirements of the Securities Act or the
Exchange Act, as applicable, and the rules and regulations of the Commission
thereunder, and none of such documents contained an untrue statement of a
material fact or omitted to state a material fact required to be stated therein
or necessary to make the statements therein, not misleading; and any further
documents so filed and incorporated or deemed to be incorporated by reference in
the Prospectus, when such documents become effective or are filed with the
Commission, as the case may be, will conform in all material respects to the
requirements of the Securities Act or the Exchange Act, as applicable, and the
rules and regulations of the Commission thereunder and will not contain an
untrue statement of a material fact or omit to state a material fact required to
be stated therein or necessary to make the statements therein not misleading.

          (e)  The Company and Thermo Electron and each of their respective
Subsidiaries have been duly incorporated and are validly existing as
corporations in good standing under the laws of their respective jurisdictions
of incorporation. The Company, Thermo Electron and each of their respective
Subsidiaries are duly qualified to do business and are in good standing as
foreign corporations in each jurisdiction in which their respective ownership or
lease of property or the conduct of their respective businesses requires such
qualification, except where the failure to be so qualified and in good standing
would not have a material adverse effect on the consolidated financial
condition, shareholders' equity, results of operations or business of such
corporation (meaning herein the Company or Thermo Electron, as the case may be)
and its Subsidiaries taken as a whole, and where so qualified have all corporate
power and authority necessary to own, lease or operate their respective
properties and to conduct the businesses in which they are engaged as described
in the Prospectus.  Except as described in the Prospectus, the Company, Thermo
Electron and their respective Subsidiaries hold all material licenses,
certificates and permits from governmental authorities necessary for the conduct
of their respective businesses as described in the Prospectus.

          (f)  The Company and Thermo Electron had an authorized and issued
capitalization as set forth in the Prospectus (as of the date specified
therein), and all of the issued and outstanding shares of capital stock of the
Company and Thermo Electron have been duly and validly authorized and issued,
are fully paid and non-assessable and conform in all material respects to the
description thereof contained in the Prospectus; and all of the issued and
outstanding shares of capital stock of each Subsidiary of the Company have been
duly and validly authorized and issued and are fully paid and non-assessable and
(except for directors' qualifying shares, as set forth in the Prospectus and
certain shares owned by Thermo Electron or any of its Subsidiaries) are owned
directly or indirectly by the Company, free and clear of all liens,
encumbrances, equities or claims, except that certain of such shares are
reserved for transfer pursuant to stock option and other benefit plans under
which options to purchase common stock of such corporation owned by its
corporate parent or Thermo Electron or any of its Subsidiaries are granted to
certain employees, directors or consultants of Thermo Electron, the Company and
their Subsidiaries.

 
                                      -5-

          (g)  If the Offered Securities are Debt Securities:  The Debt
Securities have been duly and validly authorized by the Company and, when duly
executed, issued and delivered by the Company, and authenticated by the Trustee
pursuant to the provisions of the Senior Indenture or the Subordinated
Indenture, as the case may be, against payment therefor as provided in this
Agreement, will constitute valid and legally binding obligations of the Company
entitled to the benefits of the Indenture and enforceable against the Company in
accordance with their terms, subject to the effects of bankruptcy, insolvency,
fraudulent conveyance and transfer, reorganization, moratorium, or other similar
laws now or hereafter in effect relating to creditors' rights generally
("applicable bankruptcy laws") and general equitable principles (whether
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considered in a proceeding in equity or at law); and the Debt Securities, when
issued and delivered, will conform in all material respects to the description
thereof contained in the Prospectus.  The Guarantees have been duly and validly
authorized by Thermo Electron and, when duly executed, issued and delivered by
Thermo Electron, and, if required, authenticated by the Trustee pursuant to the
provisions of the Indenture, against payment for the Debt Securities as provided
in this Agreement, will constitute valid and legally binding obligations of
Thermo Electron entitled to the benefits of such Indenture and enforceable
against Thermo Electron in accordance with their terms, subject to the effects
of applicable bankruptcy laws and general equitable principles (whether
considered in a proceeding in equity or at law); and the Guarantees, when issued
and delivered, will conform in all material respects to the description thereof
contained in the Prospectus.

          (h)  If the Offered Securities are Debt Securities: Each Indenture has
been duly authorized by the Company and Thermo Electron, and when duly executed
by the proper officers of the Company and Thermo Electron (assuming due
execution and delivery by the Trustee) and delivered by the Company and Thermo
Electron will constitute a valid and legally binding obligation of the Company
and Thermo Electron enforceable against them in accordance with its terms,
subject to the effects of applicable bankruptcy laws and general equitable
principles (whether considered in a proceeding in equity or at law); and each
Indenture conforms in all material respects to the description thereof contained
in the Prospectus.

          (i)  If the Offered Securities are shares of Common Stock:  The
unissued shares of Common Stock have been duly and validly authorized and, when
issued and delivered against payment therefor as provided in this Agreement,
such shares will be duly and validly issued, fully paid and non-assessable and
will conform in all material respects to the description thereof contained in
the Prospectus.

          (j)  If the Offered Securities are convertible into shares of Common
Stock: The shares of Common Stock reserved for issuance upon conversion of
convertible Debt Securities have been validly authorized and reserved for such
purpose; and, if and when any of such convertible Debt Securities are converted
into shares of Common Stock in accordance with the conversion rights so
provided, such shares of Common Stock will be validly  issued, fully paid and
non-assessable and delivered in accordance with the terms of the Company's
corporate charter and by-laws; and when issued and delivered, such Common Stock
will conform in all material respects to the description thereof contained in
the Prospectus.

 
                                      -6-

          (k)  If the Offered Securities are shares of Common Stock: There are
no preemptive or other rights to subscribe for or to purchase, nor any
restrictions upon the voting or transfer of any shares of the Common Stock,
including any Common Stock issuable upon conversion of any Offered Securities,
in each case, pursuant to the Company's corporate charter or by-laws or any
agreement or other instrument to which the Company is a party.

          (l)  This Agreement has been duly authorized, executed and delivered
by the Company and Thermo Electron.

          (m)  The execution, delivery and performance of this Agreement by the
Company and Thermo Electron, the execution, delivery and performance of each
Indenture (if the Offered Securities are Debt Securities) by the Company and
Thermo Electron, and the consummation of the transactions contemplated hereby
and thereby, and the issuance and delivery of the Offered Securities will not
conflict with or result in a breach or violation of any of the terms or
provisions of, or constitute a default under any indenture, lien, charge or
encumbrance upon any property or mortgage, deed of trust, loan agreement, or
other agreement or instrument to which the Company or Thermo Electron or any of
their respective Subsidiaries is a party or by which it or any of them is bound
or to which any of the property or assets of the Company or Thermo Electron or
any of their respective Subsidiaries is subject, except in each case for such
conflicts, breaches, violations or defaults which would not have a material
adverse effect on the consolidated financial condition, shareholders' equity,
results of operations or business of such corporation and its Subsidiaries taken
as a whole, nor will such action result in any violation of the provisions of
the charter or by-laws of any of such corporation or any of their respective
Subsidiaries or any statute or any order, rule or regulation of any court or
governmental agency or body having jurisdiction over the Company or Thermo
Electron or any of their respective Subsidiaries or any of their respective
material properties or assets; and except for the registration of the Offered
Securities under the Securities Act, the qualification of each Indenture under
the Trust Indenture Act, and such consents, approvals, authorizations,
registrations or qualifications as may be required under the Exchange Act or
applicable state or foreign securities laws or by the National Association of
Securities Dealers, Inc.  in connection with the purchase and distribution of
the Offered Securities by the Underwriters, no consent, approval, authorization
or order of, or filing, registration or qualification of or with, any such court
or governmental agency or body is required for the execution, delivery and
performance of this Agreement and the Indentures (if the Offered Securities are
Debt Securities) by the Company or Thermo Electron and the consummation by the
Company and Thermo Electron of the transactions contemplated hereby and thereby.

          (n)  Except as described in the Registration Statement or the
Prospectus there are no agreements or understandings between the Company and any
person granting such person the right to require the Company to file a
registration statement under the Securities Act with respect to any securities
of the Company owned or to be owned by such person or to require the Company to
include such securities in the securities registered pursuant to the
Registration Statement or in any securities being registered pursuant to any
other registration statement filed by the Company under the Securities Act.

 
                                      -7-

          (o)  Neither the Company nor any of its Subsidiaries, nor Thermo
Electron nor any of its Subsidiaries has sustained, since the date of the latest
financial statements included or incorporated by reference in the Prospectus,
any loss or interference with its business from fire, explosion, flood or other
calamity, whether or not covered by insurance, or from any labor
dispute or court or governmental action, order or decree, which is material to
the Company and its Subsidiaries taken as a whole, or to Thermo Electron and its
Subsidiaries taken as a whole, as the case may be, otherwise than as set forth
or contemplated in the Prospectus; except as contemplated by or disclosed in the
Prospectus, since such date, neither the Company nor Thermo Electron has
incurred any material liability or obligation, or entered into any material
transaction, or declared or paid any dividend on its capital stock or issued or
granted any securities; and except as contemplated by or disclosed in the
Prospectus, since such date, there has not been any material change in the
capital stock of the Company or any of its Subsidiaries or of Thermo Electron or
any of its Subsidiaries or any material change in the consolidated long-term
debt of the Company or of Thermo Electron, or any material adverse change, or
any development involving a prospective material adverse change, in or affecting
the business, management, financial condition, shareholders' equity or results
of operations of the Company and its Subsidiaries taken as a whole, or of Thermo
Electron and its Subsidiaries taken as a whole, otherwise than as set forth or
contemplated in the Prospectus.

          (p)  Arthur Andersen LLP, which has certified the financial statements
of the Company and Thermo Electron included in the Registration Statement, and
any other accounting firm which has certified any financial statements contained
in the Registration Statement, and whose reports appear in the Prospectus or are
incorporated by reference therein, are independent public accountants as
required by the Securities Act and the Rules and Regulations.

          (q)  The financial statements (including the related notes and
supporting schedules) filed as part of the Registration Statement or included or
incorporated by reference in the Prospectus present fairly in all material
respects the financial condition and results of operations of the entities
purported to be shown thereby at the dates and for the periods indicated; and
have been prepared in conformity with United States generally accepted
accounting principles or International Accounting Standards, as the case may be,
applied on a consistent basis throughout the periods involved, except as
otherwise expressly set forth therein.

          (r)  Except as described in the Prospectus, there are no legal or
governmental proceedings pending or threatened by or against the Company or
Thermo Electron or any of their respective Subsidiaries or of which any material
property or assets of the Company or Thermo Electron or any of their respective
Subsidiaries is the subject which are required to be disclosed in the
Registration Statement or the Prospectus.

          (s)  There are no contracts or other documents which are required to
be described in the Prospectus or filed as exhibits to the Registration
Statement by the Securities Act or by the Rules and Regulations which have not
been described in the Prospectus or filed as exhibits to the Registration
Statement or incorporated therein by reference under the Rules and Regulations.

          (t)  Neither the Company, Thermo Electron nor any of their respective
Subsidiaries is

 
                                      -8-

               (i)   in violation in any material respect of its corporate
charter or by-laws, or

               (ii)  except as described in the Prospectus, in default in any
material respect, and no event has occurred which, with notice or lapse of time
or both, would constitute such a default, in the due performance or observance
of any term, covenant or condition contained in any material indenture,
mortgage, deed of trust, loan agreement or other agreement to which the Company
or Thermo Electron or any of their respective Subsidiaries is a party or by
which it or any of them is or may be bound or to which any of the properties or
assets of the Company or Thermo Electron or any of their respective Subsidiaries
is subject, except for such defaults which would not have a material adverse
effect on the consolidated financial condition, shareholders' equity, results of
operations or business of the Company and its Subsidiaries taken as a whole and
Thermo Electron and its Subsidiaries taken as a whole, as the case may be; or

               (iii) except as described in the Prospectus, in violation in any
material respect of any law, ordinance, governmental rule, regulation or court
decree to which the Company or Thermo Electron or any of their respective
Subsidiaries or its or any of their respective property or assets may be subject
or has failed to obtain any material license, permit, certificate, franchise or
other governmental authorization or permit necessary to the ownership of its or
their property or to the conduct of its or their business, except for such
violations or failures which would not reasonably be expected to have a material
adverse effect on the consolidated financial condition, shareholders' equity,
results of operations or business of the Company and its Subsidiaries taken as a
whole and Thermo Electron and its Subsidiaries taken as a whole, as the case may
be.

          (u)  Except as described in the Prospectus, the Company and Thermo
Electron and their respective Subsidiaries own, or have valid rights to use, all
items of real and personal property which are material to the business of the
Company and its Subsidiaries taken as a whole and Thermo Electron and its
Subsidiaries taken as a whole, as the case may be, free and clear of all liens,
encumbrances and claims which may materially interfere with the consolidated
financial condition, shareholders' equity, results of operations or business of
such corporation and its Subsidiaries taken as a whole.

          (v)  Except as described in the Prospectus, the Company and Thermo
Electron and their respective Subsidiaries own or possess adequate licenses or
other rights to use all intellectual property rights, including patents,
trademarks, service marks, trade names, copyrights or know-how, necessary to
conduct their respective businesses as described in the Prospectus, except where
such failure, singularly or in the aggregate, would not have a material adverse
effect on the consolidated financial condition, shareholders' equity, results of
operations or business of the Company and its Subsidiaries taken as a whole and
Thermo Electron and its Subsidiaries taken as a whole, as the case may be, and,
except as described in the Prospectus, none of the Company or Thermo Electron or
their respective Subsidiaries has received any notice of infringement of or
conflict with (or knows of any such infringement of or conflict with) rights or
claims of others with respect to any patents, patent applications, trademarks,
service marks, trade names, copyrights or know-how, that is reasonably likely to
result in a material adverse effect on the consolidated financial condition,
shareholders' equity, results of operations 

 
                                      -9-

or business of the Company and its Subsidiaries taken as a whole and Thermo
Electron and its Subsidiaries taken as a whole, as the case may be.

          (w)  Neither the Company, nor Thermo Electron, nor any of their
respective Subsidiaries,  is an "investment company" within the meaning of such
term under the Investment Company Act of 1940 and the rules and regulations of
the Commission thereunder.

          (x)  Since the date which is three months prior to this Agreement, no
debt rating assigned to Thermo Electron by any "nationally recognized
statistical rating organization," as that term is defined by the Commission for
purposes of Rule 436(g)(2) of the Rules and Regulations, has been lowered or, to
Thermo Electron's knowledge, threatened to be lowered by any such rating
organization nor, to Thermo Electron's knowledge, has it been placed under
surveillance or review by any such rating organization.

          (y)  Any certificate signed by any officer of the Company or Thermo
Electron and delivered to the Underwriters or to counsel for the Underwriters
pursuant to this Agreement shall be deemed a representation and warranty
hereunder by the Company or Thermo Electron, as the case may be, to each
Underwriter as to the matters covered thereby.

     2.   Purchase of the Offered Securities by the Underwriters.  On the
          ------------------------------------------------------         
basis of the representations and warranties contained in, and subject to the
terms and conditions set forth herein, the Company agrees to sell to the
Underwriters and each of the Underwriters, severally and not jointly, agrees to
purchase from the Company, at the price and/or principal amount, as the case may
be, set forth in the applicable Terms Agreement and in the respective amounts
and number of shares, as the case may be, of the designated Offered Securities
set forth opposite the name of each such Underwriter in Exhibit A to such Terms
                                                        ---------              
Agreement.  In addition, the Company may specify in any Terms Agreement relating
to any offering that the Company thereby grants to the Underwriters an option to
purchase up to the number of shares or principal amount of additional Offered
Securities (the "Option Securities," and if so purchased shall also be "Offered
                 -----------------                                      -------
Securities" herein) in the amount set forth in such Terms Agreement.  The option
- ----------                                                                      
thereby granted is exercisable as provided in Section 4 hereof, shall expire at
the close of business on the 30th day after the date of the applicable Terms
Agreement (unless otherwise specified therein) and will be granted solely for
the purpose of covering over-allotments which may be made in connection with the
applicable offering.  The Option Securities shall be purchased severally for the
account of the Underwriters in proportion to the number or amount of Offered
Securities set opposite the name of such Underwriters in Exhibit A of the
                                                         ---------       
applicable Terms Agreement.  The respective purchase obligations of each
Underwriter with respect to the Option Securities shall be adjusted by the
managing Underwriter so that no Underwriter shall be obligated to purchase
Option Securities in amounts other than in 100 share or $1,000 principal amount
increments.

     3.   Offering of the Offered Securities by the Underwriters.  
          ----------------------------------------- ------------          
          (a)  The several Underwriters propose to offer the Offered
Securities for sale upon the terms and conditions set forth in the Prospectus
and any amendment or supplement thereto relating to the Offered Securities.

 
                                      -10-

          (b)  Each Underwriter severally agrees to comply with the
following restrictions in the offering and sale of any Debt Securities:

               (i)   except to the extent permitted under U.S. Treasury
Regulation (S)1.163-5(c)(2)(i)(D) (the  "D Rules"), (A) the Underwriters have 
                                         ------- 
not offered or sold, and during the restricted period will not offer or sell,
Debt Securities in bearer form to a person who is within the United States or
its possessions or to a United States person, and (B) the Underwriters have not
delivered, and will not deliver, within the United States or its possessions
definitive Debt Securities in bearer form that are sold during the restricted
period;

               (ii)  The Underwriters and each of their affiliates that is
acquiring from them Debt Securities in bearer form for the purposes of offering
or selling such Debt Securities during the restricted period, presently have in
effect, and throughout the restricted period will have in effect, procedures
reasonably designed to ensure that such Underwriters and such affiliates and
their respective employees or agents who are directly engaged in selling Debt
Securities in bearer form are aware that such Debt Securities may not be offered
or sold during the restricted period to a person who is within the United States
or its possessions or to a United States person, except as permitted by the D
Rules;

               (iii) Each Underwriter that is a United States person, if
any, is acquiring, either as agent or on its own behalf, the Debt Securities in
bearer form for purposes of resale in connection with their original issuance,
and if it retains Debt Securities in bearer form for its own account, it will
only do so in accordance with the requirements of U.S. Treasury Regulation
(S)1.163-5(c)(2)(i)(D)(6); and

               (iv)  With respect to each of the Underwriters' affiliates
that acquires from such Underwriter Debt Securities in bearer form for the
purpose of offering or selling such Debt Securities during the restricted
period, such Underwriter agrees that it will obtain from such affiliate for the
benefit of the Company the representations, warranties, covenants and agreements
contained in clauses (i), (ii) and (iii).

Terms used in this Section 3(b) have the meanings given to them by the U.S.
Internal Revenue Code and regulations thereunder, including the D Rules.

          (c)  Each Underwriter severally represents and agrees that (i) it has
not offered or sold and will not offer or sell in the United Kingdom any Offered
Securities except to persons whose ordinary activities involve them in
acquiring, holding, managing or disposing of investments (as principal or agent)
for the purpose of their businesses or otherwise in circumstances which have not
resulted and will not result in an offer to the public in the United Kingdom
within the meaning of the Public Offers of Securities Regulations 1995 (the
"Regulations") or the Financial Services Act 1986, (ii) it has complied and will
 ------------
comply with all applicable provisions of the Financial Services Act 1986 and the
Regulations with respect to anything done by it in relation to the Offered
Securities in, from or otherwise involving the United Kingdom and (iii) it has
only issued or passed on, and will only issue or pass on, in the United Kingdom
any document 

 
                                      -11-

received by it in connection with the issue of the Offered Securities if that
person is of a kind described in Article 11(3) of the Financial Services Act
1986 (Investment Advertisements) (Exemptions) Order 1996, as amended by article
4 of the Financial Services Act 1986 (Investment Advertisements) (Exemptions)
Order 1997, or is a person to whom the document may otherwise lawfully be issued
or passed on.

          (d)  Each Underwriter, jointly and severally, represents and warrants
that they have not entered into, and agree that they will not enter into, any
contractual arrangement with respect to the distribution or delivery of the Debt
Securities in bearer form, except with their respective affiliates, without the
prior written consent of the Company or pursuant to a form of selling agreement
containing restrictions substantially to the effect set forth in paragraph (b)
above.

     4.   Delivery of and Payment for the Offered Securities.  Delivery of
          --------------------------------------------------
and payment for the Offered Securities shall be made at the headquarters office
of the managing Underwriter, or at such other location as may be agreed upon by
the Underwriters and the Company, at 10:00 a.m., Eastern time, on the third
business day (or on the fourth business day, if permitted by the Rules and
Regulations) following the date of this Agreement, or at such other time and
date as shall be agreed upon (each such date and time of payment and delivery
being herein called the "Closing Date") in the manner set forth in the
                         ------------                                 
applicable Terms Agreement.  Time shall be of the essence, and delivery at the
time and place specified pursuant to this Agreement is a further condition of
the obligation of each Underwriter hereunder. Upon delivery, the Offered
Securities shall be registered in such names and in such denominations as the
Underwriters shall request in writing not less than two full business days prior
to the Closing Date.  For the purpose of expediting the checking and packaging
of the certificates for the Common Stock, the Company shall make the
certificates representing the Common Stock available for inspection by the
Underwriters in New York, New York, not later than 2:00 p.m., Eastern time, on
the business day prior to the Closing Date.  The Debt Securities of a series may
be issued in whole or in part in the form of one or more global securities that
will be deposited with, or on behalf of, one or more depositories, or a nominee
thereof, identified in the Prospectus relating to such series.  In such a case,
the manner of delivery of such global securities will be set forth in the
applicable Terms Agreement, or if not so set forth, as described in the
applicable Prospectus.  At any time on or before the thirtieth day after the
date of any Terms Agreement relating to Option Securities, if applicable, the
option granted in Section 2 may be exercised by written notice being given to
the Company by or on behalf of the Underwriters.  Such notice shall set forth
the aggregate number or amount of Option Securities as to which the option is
being exercised, the names in which the Option Securities are to be registered
if not in global form as set forth above, the denominations in which the shares
of Option Securities are to be issued and the date and time, as determined by
the Underwriters, when the Option Securities are to be delivered; provided,
however, that this date and time shall not be earlier than the Closing Date nor
earlier than the second business day after the date on which the option shall
have been exercised nor later than the third business day after the date on
which the option shall have been exercised.  The date and time the Option
Securities are delivered are sometimes referred to as the "Option Closing Date".
                                                           -------------------
Delivery of and payment for the Option Securities shall be made at the place
specified in the first sentence of the first paragraph of this Section 4 (or at
such other place as shall be determined by agreement between the Underwriters
and the Company at 10:00 a.m., Eastern time, on the Option Closing Date).  On

 
                                      -12-

the Option Closing Date, the Company shall deliver or cause to be delivered the
certificates representing the Option Securities to the Underwriters for the
account of each Underwriter against payment to or upon the order of the Company
of the purchase price in the manner set forth in the applicable
Terms Agreement.  Time shall be of the essence, and delivery at the time and
place specified pursuant to this Agreement is a further condition of the
obligation of each Underwriter hereunder.  Upon delivery, the Option Securities
shall be registered in such names (if other than in global form) and in such
denominations as the Underwriters shall request in the aforesaid notice.  For
the purpose of expediting the checking and packaging of certificates for the
Option Securities that are Common Stock, the Company shall make the certificates
representing such Common Stock available for inspection by the Underwriters in
New York, New York, not later than 2:00 p.m., Eastern time, on the business day
prior to the Option Closing Date.

     5.   Further Agreements of the Company and Thermo Electron.  The Company 
          -----------------------------------------------------
and Thermo Electron each agree:

          (a)  To prepare the Prospectus in a form reasonably approved by the
Underwriters and to file such Prospectus pursuant to Rule 424(b) under the
Securities Act not later than the Commission's close of business on the second
business day following the execution and delivery of the applicable Terms
Agreement or, if applicable, such earlier time as may be required by Rule
430A(a)(3) under the Securities Act; after the date of  the applicable Terms
Agreement, to make no further amendment or supplement to the Registration
Statement or to the Prospectus prior to the applicable Closing Date except as
permitted herein; to advise the Underwriters, promptly after it receives notice
thereof, of the time when any amendment to the Registration Statement has been
filed or becomes effective or any supplement to the Prospectus or any amended
Prospectus has been filed and to furnish the Underwriters with copies thereof;
to file promptly all reports and any definitive proxy or information statements
required to be filed by the Company or Thermo Electron with the Commission
pursuant to Section 13(a), 13(c), 14 or 15(d) of the Exchange Act subsequent to
the date of the Prospectus and for so long as the delivery of a prospectus is
required in connection with the offering or sale of the Offered Securities; to
advise the Underwriters, promptly after it receives notice thereof, of the
issuance by the Commission of any stop order or of any order preventing or
suspending the use of any Preliminary Prospectus or the Prospectus, of the
suspension of the qualification of the Offered Securities for offering or sale
in any jurisdiction, of the initiation or threatening of any proceeding for any
such purpose, of any request by the Commission for the amending or supplementing
of the Registration Statement or the Prospectus or for additional information;
and, in the event of the issuance of any stop order or of any order preventing
or suspending the use of any Preliminary Prospectus or the Prospectus or
suspending any such qualification, to use promptly its best efforts to obtain
its withdrawal;

          (b)  To furnish, promptly upon request by the representatives of the
Underwriters named in any applicable Terms Agreement (the "Representatives" and
                                                           ---------------     
if no Representatives are so named, then any references herein to the
Representatives shall be deemed to refer to the Underwriters), to the
Underwriters and to counsel for the Underwriters a copy of the Registration
Statement as originally filed with the Commission, and each amendment thereto
filed with the Commission, including all consents and exhibits filed therewith;

 
                                      -13-

          (c)  To deliver promptly to the Underwriters such number of the
following documents as the Representatives shall reasonably request:

               (i)   conformed copies of the Registration Statement as
originally filed with the Commission and each amendment thereto (in each case
excluding exhibits other than this Agreement and the Indentures and such other
exhibits as the Underwriters may reasonably request),

               (ii)  each Preliminary Prospectus, the Prospectus and any amended
or supplemented Prospectus; and

               (iii) any document incorporated or deemed incorporated by
reference in the Prospectus (excluding exhibits thereto); and, if the delivery
of a prospectus is required at any time after the Effective Date in connection
with the offering or sale of the Offered Securities and if at such time any
events shall have occurred as a result of which the Prospectus as then amended
or supplemented would include an untrue statement of a material fact or omit to
state any material fact necessary in order to make the statements therein, in
the light of the circumstances under which they were made when such Prospectus
is delivered, not misleading, or, if for any other reason it shall be necessary
to amend or supplement the Prospectus (or to file under the Exchange Act any
document incorporated by reference in the Prospectus) in order to comply with
the Securities Act or the Exchange Act, to notify the Underwriters and, upon the
reasonable request of the Representatives, to file such document and to prepare
and furnish without charge to each Underwriter as many copies as the
Representatives may from time to time reasonably request of an amended or
supplemented Prospectus which will correct such statement or omission or effect
such compliance;

          (d)  To file promptly with the Commission any amendment to the
Registration Statement or the Prospectus or any supplement to the Prospectus
that may, in the judgment of the Company, Thermo Electron and the Underwriters,
be required by the Securities Act, or requested by the Commission;

          (e)  Prior to filing with the Commission any amendment to the
Registration Statement or supplement to the Prospectus, and promptly after
filing with the Commission (or, if between the signing of any applicable Terms
Agreement and the Closing Date thereunder, prior to filing with the Commission)
any document incorporated or deemed incorporated by reference in the Prospectus
or any Prospectus pursuant to Rule 424 of the Rules and Regulations, to furnish
a copy thereof to the Underwriters and counsel for the Underwriters;

          (f)  As soon as practicable after the date of this Agreement and every
Terms Agreement relating to designated Offered Securities, to make generally
available to its security holders an earnings statement of the Company and its
Subsidiaries, and if the applicable Offered Securities include Guarantees, an
earnings statement of Thermo Electron and its Subsidiaries (which, in each case,
need not be audited) complying with Section 11(a) of the Securities Act and 

 
                                      -14-

the Rules and Regulations (including, at the option of the Company or Thermo
Electron, as the case may be, Rule 158);

          (g)  For a period of five years following the applicable Closing Date,
to furnish to the Underwriters, copies of all materials furnished by the Company
or Thermo Electron to all of its shareholders and all public reports and all
reports and financial statements furnished by the Company or Thermo Electron to
the principal national securities exchange upon which the Common Stock and any
other Offered Securities may be listed pursuant to requirements of or agreements
with such exchange or to the Commission pursuant to the Exchange Act or any
rules or regulations of the Commission thereunder;

          (h)  Promptly from time to time to take such action as the
Underwriters may reasonably request to qualify the Offered Securities for
offering and sale under the securities laws of such jurisdictions as the
Underwriters may reasonably request and to comply with such laws so as to permit
the continuance of sales and dealings therein in such jurisdictions for as long
as may be necessary to complete the distribution of the Offered Securities;
provided, however, that in connection therewith the Company and Thermo Electron
shall not be required to qualify as a foreign corporation or to file a general
consent to service of process in any jurisdiction where it is not so qualified;

          (i)  For a period of 90 days after the date of the Prospectus relating
to designated  Common Stock, or Offered Securities convertible into Common Stock
but only if specified in the applicable Terms Agreement (unless a different time
period is set forth in the applicable Terms Agreement), the Company and Thermo
Electron will not, directly or indirectly, offer for sale, sell or otherwise
dispose of (or enter into any hedging transaction or device which is designed
to, or could be expected to, result in the disposition by any person at any time
in the future of) any shares of Common Stock or any security convertible or
exchangeable for Common Stock (other than shares sold to Thermo Electron or its
Subsidiaries or shares issuable pursuant to employee benefit plans, stock option
plans or other compensation plans existing on the date thereof or pursuant to
then currently outstanding options, warrants or rights and other than the
issuance of shares of Common Stock as consideration for the acquisition of one
or more businesses provided that such Common Stock may not be resold prior to
the expiration of the 90-day period referenced above), or sell or grant options,
rights or warrants with respect to any shares of Common Stock (other than the
grant of options pursuant to option plans existing on the date thereof)
otherwise than in accordance with this Agreement without the prior written
consent of the Representatives;

          (j)  In the event designated Offered Securities are to be listed on a
securities exchange, to apply for any listing of such designated Offered
Securities on such securities exchange and to use its best efforts to complete
and maintain that listing, subject only to official notice of issuance, prior to
the relevant Closing Date, or if not so listed by such date, as soon as
practical thereafter. In the case of Offered Securities that are Debt Securities
to be listed on a foreign securities exchange, if the Company is not able to
effect or maintain such listing, it will use its best efforts to obtain and
maintain the quotation for, or listing of, such Debt Securities on 

 
                                      -15-

such other stock exchange or exchanges as the Company may, with the approval of
the Representatives, determine;

          (k)  To apply the net proceeds from the sale of the Offered
Securities being sold by the Company as set forth in the Prospectus; and

          (l)  If the Offered Securities include Debt Securities, not to offer
or sell such Debt Securities in bearer form during the restricted period to a
person who is within the United States or its possessions or to a United States
person (each as defined in the U.S. Internal Revenue Code and regulations
thereunder, including the D Rules).

     6.   Expenses.  The Company agrees to pay:
          --------                     

          (a)  the costs incident to the authorization, issuance, sale and
delivery of the Offered Securities and any taxes payable in that connection
(other than taxes based on income);

          (b)  the costs incident to the preparation, printing and filing under
the Securities Act of the Registration Statement and any amendments and exhibits
thereto;

          (c)  the costs of distributing the Registration Statement as
originally filed and each amendment thereto and any post-effective amendments
thereof (including, in each case, exhibits), any Preliminary Prospectus, the
Prospectus and any amendment or supplement to the Prospectus or any document
incorporated or deemed incorporated by reference therein, all as provided in
this Agreement;

          (d)  the costs, if any, of printing this Agreement and any other
related documents in connection with the offering, purchase, sale and delivery
of the Offered Securities;

          (e)  any applicable listing or other fees;

          (f)  the filing fee of the National Association of Securities Dealers,
Inc. and the fees and expenses of qualifying the Offered Securities under the
securities laws of the several jurisdictions as provided in Section 5(h) and of
preparing, printing and distributing a Blue Sky Memorandum and a Legal
Investment Survey (including related fees and expenses of counsel to the
Underwriters);

          (g)  any fees charged by securities rating services for rating any
Offered Securities; and

          (h)  all other costs and expenses incident to the performance of the
obligations of the Company and Thermo Electron under this Agreement; provided
that, except as provided in this Section 6 and in Section 8 and Section 11, the
Underwriters shall pay the costs and expenses of their counsel, any transfer
taxes on the Offered Securities which they may sell, the expenses of advertising
any offering of the Offered Securities made by the Underwriters and all other
costs and expenses of the Underwriters and their counsel not enumerated in this
Section 6.

 
                                      -16-

     7.   Conditions of Underwriters' Obligations.  The obligations of the
          ---------------------------------------                         
Underwriters to purchase and pay for any Offered Securities are subject to the
accuracy, when made, and on each Closing Date, of the representations and
warranties of the Company and Thermo Electron contained herein, to the
performance by the Company and Thermo Electron of their respective
obligations hereunder and under any Terms Agreement, and to each of the
following additional terms and conditions:

          (a)  At the applicable Closing Date, the Prospectus shall have been
timely filed with the Commission in accordance with Section 5(a); no stop order
suspending the effectiveness of the Registration Statement or any part thereof
shall have been issued and no proceeding for that purpose shall have been
initiated or threatened by the Commission; and any request of the Commission for
inclusion of additional information in the Registration Statement or the
Prospectus or otherwise shall have been complied with to the Representatives'
reasonable satisfaction.

          (b)  No Underwriter shall have discovered and disclosed to the Company
on or prior to any Closing Date that the Registration Statement or the
Prospectus or any amendment or supplement thereto contains an untrue statement
of a fact that, in the opinion of counsel for the Underwriters, is material or
omits to state a fact that, in the opinion of such counsel, is material and is
required to be stated therein or is necessary to make the statements therein (in
the case of the Prospectus, in light of the circumstances in which they were
made), not misleading.

          (c)  All corporate proceedings and other legal matters incident to the
authorization, form, validity and enforceability of this Agreement, any Terms
Agreement, the Indentures, the Offered Securities, the Registration Statement
and the Prospectus, and all other legal matters relating to this Agreement and
any Terms Agreement and the transactions contemplated hereby and thereby shall
be reasonably satisfactory in all material respects to counsel for the
Underwriters, and the Company and Thermo Electron shall have furnished to such
counsel all documents and information that they may reasonably request to enable
them to pass upon such matters.

          (d)  Seth H. Hoogasian, Esq., General Counsel to the Company and
Thermo Electron, shall have furnished to the Underwriters his opinion, in such
capacities, addressed to the Underwriters and dated the Closing Date, in form
and substance reasonably satisfactory to counsel for the Underwriters, to the
effect that:

               (i)   The Company and Thermo Electron and each of their
respective Significant Subsidiaries have been duly incorporated and are validly
existing as corporations in good standing under the laws of their respective
jurisdictions of incorporation. The Company, Thermo Electron and each of their
respective Significant Subsidiaries are duly qualified to do business and are in
good standing as foreign corporations in each jurisdiction in which their
respective ownership or lease of property or the conduct of their respective
businesses requires such qualification except where the failure to be so
qualified and in good standing would not have a material adverse effect on the
consolidated financial condition, shareholders' equity,

 
                                      -17-

results of operations or business of such corporation and its Subsidiaries taken
as a whole, and have all corporate power and authority necessary to own, lease
or operate their respective properties and to conduct the businesses in which
they are engaged as described in the Prospectus;

               (ii)  The Company and Thermo Electron have an authorized
capitalization as set forth in the Prospectus (as of the date such information
is given). All of the outstanding shares of capital stock of each of the
Company, Thermo Electron and their respective Significant Subsidiaries are duly
authorized and validly issued, and, to the best of such counsel's knowledge,
fully paid and non-assessable; to the best of such counsel's knowledge, the
Company and Thermo Electron own, directly or indirectly through Subsidiaries,
the amount of the outstanding capital stock of their respective Significant
Subsidiaries, as described in the Prospectus (as of the date such information is
given), and to the best of such counsel's knowledge, such ownership is free and
clear of any lien, claim or encumbrance or any other claim of any third party
(except for certain obligations of the Company, Thermo Electron or their
Subsidiaries, as the case may be, pursuant to their stock and employee benefit
plans). To the best of such counsel's knowledge, except as described in the
Prospectus, including options granted or to be granted pursuant to stock and
employee benefit plans described therein, there are no outstanding warrants or
options to purchase any shares of the capital stock of the Company from the
Company and there are no outstanding warrants or options to purchase any shares
of capital stock of Thermo Electron from Thermo Electron to persons other than
Subsidiaries of Thermo Electron. There are no preemptive or other rights to
subscribe for or to purchase, nor any restriction upon the voting or transfer
of, any shares of the Common Stock, including any Common Stock issuable upon
conversion of any Offered Securities, in each case pursuant to the Company's
corporate charter or by-laws or any agreement or other instrument to which the
Company is a party known to such counsel;

               (iii) To the best of such counsel's knowledge, there are no
contracts or other documents which are required to be described in the
Prospectus or filed as exhibits to the Registration Statement by the Securities
Act or by the Rules and Regulations which have not been described in the
Prospectus or filed as exhibits to the Registration Statement or incorporated
therein by reference under the Rules and Regulations;

               (iv)  The documents incorporated by reference in the Prospectus
(other than the financial statements and related schedules therein, as to which
such counsel need express no opinion), when they were filed with the Commission
complied as to form in all material respects with the requirements of the
Exchange Act and the rules and regulations of the Commission thereunder;

               (v)   Except as described in Section 1(o) hereof, to the best of
such counsel's knowledge and except as described in the Prospectus, there are no
agreements or understandings between the Company and any person granting such
person the right to require the Company to file a registration statement under
the Securities Act with respect to any securities of the Company owned or to be
owned by such person or to require the Company to include such securities in the
securities registered pursuant to the Registration Statement or in 

 
                                      -18-



any securities being registered pursuant to any other registration statement
filed by the Company under the Securities Act;

               (vi) To the best of such counsel's knowledge, and other than as
set forth in the Registration Statement or the Prospectus, there are no legal or
governmental proceedings pending or threatened by or against the Company or
Thermo Electron or any of their respective Subsidiaries or of which any material
property or assets of the Company or Thermo Electron or any of their respective
Subsidiaries is the subject which are required to be disclosed in the
Registration Statement or the Prospectus;

              (vii) If the Offered Securities are Debt Securities:  The Debt
Securities have been duly and validly authorized by the Company and, when duly
executed, issued and delivered by the Company, and authenticated by the Trustee
pursuant to the provisions of each Indenture, against payment therefor as
provided in this Agreement, will constitute valid and legally binding
obligations of the Company entitled to the benefits of such Indenture and
enforceable against the Company in accordance with their terms, except as the
enforceability thereof may be limited by applicable bankruptcy laws and by
general equitable principles (regardless of whether the issue of enforceability
is considered in a proceeding in equity or at law), and the Debt Securities
conform as to legal matters in all material respects to the description thereof
contained in the Prospectus. The Guarantees have been duly and validly
authorized by Thermo Electron and, when duly executed, issued and delivered by
Thermo Electron, against payment for the Debt Securities as provided in this
Agreement, will constitute valid and legally binding obligations of Thermo
Electron entitled to the benefits of the Indenture and enforceable against
Thermo Electron in accordance with their terms, subject to the effects of
applicable bankruptcy laws and to general equitable principles (whether
considered in a proceeding in equity or at law); and the Guarantees conform as
to legal matters in all material respects to the description thereof contained
in the Prospectus.

               (viii) If the Offered Securities are Debt Securities:  Each
Indenture has been duly authorized, executed and delivered by the Company and
Thermo Electron, and (assuming due execution and delivery by the Trustee)
constitutes a valid and legally binding obligation of the Company and Thermo
Electron enforceable against the Company and Thermo Electron in accordance with
its terms, except as the enforceability thereof may be limited by applicable
bankruptcy laws and by general equitable principles (regardless of whether the
issue of enforceability is considered in a proceeding in equity or at law); and
each Indenture conforms as to legal matters in all material respects to the
description thereof contained in the Prospectus;

               (ix)   If the Offered Securities are shares of Common Stock:  The
unissued shares of the Common Stock have been duly and validly authorized and,
when issued and delivered against payment therefor as provided in this
Agreement, such shares will be duly and validly issued, fully paid and non-
assessable; and the Common Stock conforms as to legal matters in all material
respects to the description thereof contained in the Prospectus;

               (x)    If the Offered Securities are convertible into shares of
Common Stock: The Common Stock reserved for issuance upon conversion of
convertible Debt Securities

 
                                      -19-

has been validly authorized and reserved for such purpose; and, if and when any
of such convertible Debt Securities are converted into shares of Common Stock in
accordance with the conversion rights so provided, such shares of Common Stock
will be validly issued, fully paid and non-assessable and delivered in
accordance with the terms of the Company's corporate charter and by-laws;

               (xi) This Agreement has been duly authorized, executed and
delivered by the Company and Thermo Electron;

               (xii) The issue and sale of the Offered Securities being
delivered on the Closing Date by the Company and the compliance by the Company
and Thermo Electron with all of the provisions of this Agreement and each
Indenture, and the consummation of the transactions contemplated hereby and
thereby, will not conflict with or result in a breach or violation of any of the
terms or provisions of, or constitute a default under, any material indenture,
mortgage, deed of trust, loan agreement or other agreement known to such counsel
to which the Company or Thermo Electron or any of their respective Subsidiaries
is a party or by which the Company or Thermo Electron or any of such
Subsidiaries is bound or to which any of the property or assets of the Company
or Thermo Electron or any of their respective Subsidiaries is subject except for
such conflicts, breaches, violations or defaults which would not have a material
adverse effect on the consolidated financial condition, shareholders' equity,
results of operations or business of such corporation and its Subsidiaries taken
as a whole, nor will such actions result in any violation of the charter or by-
laws of the Company or Thermo Electron or any provisions of any State or Federal
statute or any order, rule or regulation known to such counsel of any court or
governmental agency or body having jurisdiction over the Company or Thermo
Electron or any of their respective Subsidiaries or any of their respective
material properties or assets (other than statutes, orders, rules and
regulations pertaining to securities laws matters, which are addressed elsewhere
in such opinion).

               (xiii) Except for the registration of the Offered Securities
under the Securities Act and such consents, approvals, authorizations,
registrations or qualifications as may be required under the Exchange Act, the
Trust Indenture Act and applicable state securities laws or by the National
Association of Securities Dealers, Inc., in connection with the purchase and
distribution of the Offered Securities by the Underwriters, no consent,
approval, authorization or order of, or filing or registration with, any such
court or governmental agency or body is required for the execution, delivery and
performance of this Agreement or the Indentures by the Company and Thermo
Electron and the consummation by the Company and Thermo Electron of the
transactions contemplated hereby and thereby.

               (xiv) The Registration Statement was declared effective under the
Securities Act and each Indenture was qualified under the Trust Indenture Act as
of the date specified in such opinion, the Prospectus was filed with the
Commission pursuant to the subparagraph of Rule 424 specified in such opinion on
the date specified therein and no stop order suspending the effectiveness of the
Registration Statement has been issued and, to the best of such counsel's
knowledge, no proceeding for that purpose is pending or threatened by the
Commission;

 
                                      -20-

               (xv) The statements contained in the Prospectus under the
captions relating to the Offered Securities, insofar as they describe federal
statutes, rules and regulations, or portions thereof (other than those
pertaining to tax matters, as to which such counsel need not express any
opinion), constitute accurate descriptions thereof in all material respects; and

               (xvi) The Registration Statement, as of the Effective Date, and
the Prospectus, as of the date it was filed with the Commission and as of the
Closing Date, and any further amendments or supplements thereto made by the
Company or Thermo Electron prior to the applicable Closing Date (other than the
financial statements and related schedules therein and all other financial and
statistical data included therein or omitted therefrom and other than the Form
T-1, as to which such counsel need express no opinion) complied as to form in
all material respects with the requirements of the Securities Act and the Rules
and Regulations; and each Indenture conforms in all material respects to the
requirements of the Trust Indenture Act and the applicable rules and regulations
thereunder.

          In rendering the foregoing opinions, such counsel may state that his
opinion is limited to matters governed by the federal laws of the United States
of America, the Delaware General Corporation Law and the laws of the
Commonwealth of Massachusetts.

          In addition, such counsel shall also have furnished to the
Underwriters a written statement, addressed to the Underwriters and dated the
Closing Date, in form and substance satisfactory to the Underwriters, to the
effect that such counsel has acted as counsel to the Company in connection with
the preparation of the Registration Statement, and based on the foregoing, such
counsel does not believe that (i) the Registration Statement (other than the
financial statements and related schedules and all other financial and
statistical data included or incorporated by reference therein or omitted
therefrom, the statements under the heading, "United States Taxation for Non-
U.S. Persons," and  the Form T-1, as to which such counsel need not express any
belief), as of the Effective Date, contained any untrue statement of a material
fact or omitted to state a material fact required to be stated therein or
necessary in order to make the statements therein not misleading, or that the
Prospectus (other than the financial statements and related schedules and all
other financial and statistical data included or incorporated by reference
therein or omitted therefrom, the statements under the heading, "United States
Taxation for Non-U.S. Persons," and  the Form T-1, as to which such counsel need
not express any belief), as of its date and the applicable Closing Date,
contains any untrue statement of a material fact or omits to state a material
fact required to be stated therein or necessary in order to make the statements
therein, in light of the   circumstances under which they were made, not
misleading or (ii) any document incorporated by reference in the Prospectus
(other than the financial statements and related schedules and all other
financial and statistical data included or incorporated by reference therein or
omitted therefrom and other than the Form T-1, as to which such counsel need not
express any belief) contained an untrue statement of a material fact or omitted
to state a material fact necessary in order to make the statements therein, in
light of the circumstances under which they were made, not misleading.  The
foregoing opinion and statement may be qualified by statements to the effect
that  such counsel does not assume any responsibility for the accuracy,
completeness or fairness of the statements contained

 
                                      -21-

in the Registration Statement or the Prospectus except for the statements made
in the Prospectus under the captions relating to the designated Offered
Securities and insofar as such statements relate to the Offered Securities and
concern legal matters (other than tax matters).

          (e) If the applicable Prospectus Supplement refers to an opinion of
tax counsel for the Company relating to tax matters concerning the Offered
Securities, the Company shall have furnished to the Underwriters an opinion of
such counsel, addressed to the Underwriters, dated the Closing Date, to the
effect that the opinion of such counsel referred to in the Prospectus is
confirmed.

          (f) At the Closing Date, counsel for the Underwriters shall have been
furnished with such documents and opinions as they may reasonably require for
the purpose of enabling them to pass upon the issuance and sale of the Offered
Securities as contemplated herein and in each Terms Agreement and related
proceedings, or in order to evidence the accuracy of any of the representations
or warranties, or the fulfillment of any of the conditions, herein and therein
contained; and the Underwriters shall have received from counsel for the
Underwriters, such opinion or opinions, dated the Closing Date, with respect to
the issuance and sale of the Offered Securities, the Registration Statement, the
Prospectus and other related matters as the Underwriters may reasonably require.

          (g) At the time of execution of  each Terms Agreement, the
Underwriters shall have received from each of Arthur Andersen LLP, with respect
to the Company and if the Offered Securities include Debt Securities, Thermo
Electron, and any other accounting firm which has audited financial statements
included in the Registration Statement, letters, in form and substance
satisfactory to the Underwriters, addressed to the Underwriters and dated the
date of such Terms Agreement (i) confirming that they are independent public
accountants with respect to the Company, Thermo Electron or such other
corporation, and their respective Subsidiaries, as the case may be, within the
meaning of the Securities Act and are in compliance with the applicable
requirements relating to the qualification of accountants under Rule 2-01 of
Regulation S-X of the Commission, (ii) stating as of the date thereof (or with
respect to matters involving changes or developments since the respective dates
as of which specified financial information is given in the Prospectus, as of a
date not more than five days prior to the date thereof), the conclusions and
findings of such firm with respect to the financial information and other
matters ordinarily covered by "accountants' comfort letters" to underwriters in
connection with registered public offerings in accordance with Statement of
Auditing Standards No. 72.

          (h) With respect to the letters of the accounting firms referred to in
the preceding paragraph and delivered to the Underwriters concurrently with the
execution of each Terms Agreement (the "initial letters"), the Company shall
                                        ---------------                     
have furnished to the Underwriters letters (the "bring-down letters") of such
                                                 ------------------          
accountants, addressed to the Underwriters and dated the Closing Date (i)
confirming that they are independent public accountants within the meaning of
the Securities Act and are in compliance with the applicable requirements
relating to the qualification of accountants under Rule 2-01 of Regulation S-X
of the Commission, (ii) stating, as of the date of the bring-down letter (or,
with respect to matters involving changes or developments since the respective
dates as of which specified financial information is given in

 
                                      -22-

the Prospectus, as of a date not more than five business days prior to the date
of the bring-down letter), the conclusions and findings of such firm with
respect to the financial information and other matters covered by the initial
letters and (iii) confirming in all material respects the conclusions and
findings set forth in the initial letters.

          (i) At each Closing Date, there shall not have been, since the
respective dates as of which information is given in the Registration Statement,
the Base Prospectus and any Preliminary Prospectus as in effect at the time of
execution of the applicable Terms Agreement, any material adverse change in the
consolidated financial condition, stockholders' equity, results of operations or
business of the Company and its Subsidiaries taken as a whole, or of Thermo
Electron and its Subsidiaries taken as a whole, whether or not arising in the
ordinary course of business, except as set forth in or contemplated by such
documents.

          (j) The Company shall have furnished to the Representatives a
certificate of the Company, signed by the Chairman of the Board, Chief Executive
Officer, the President or a Vice President and the Treasurer, Secretary or an
Assistant Secretary of the Company, dated the Closing Date, to the effect that
the signers of such certificate have carefully examined the Registration
Statement, the Prospectus, any supplements to the Prospectus and this Agreement
and that, to the best of such person's knowledge:

               (i) the representations and warranties of the Company in this
     Agreement are true and correct on and as of the date of the certificate
     with the same effect as if made on the date of the certificate, and the
     Company has complied with all the agreements and satisfied all the
     conditions on its part to be performed or satisfied at or prior to the
     Closing Date;

               (ii) no stop order suspending the effectiveness of the
     Registration Statement has been issued and no proceedings for that purpose
     have been instituted or, to such person's knowledge, threatened; and

               (iii)  since the respective dates as of which information is
     given in the Registration Statement, the Base Prospectus and any
     Preliminary  Prospectus as in effect at the time of execution of the
     applicable Terms Agreement, there has been no material adverse change in
     the consolidated financial condition, stockholders' equity, results of
     operations or business of the Company and its Subsidiaries taken as a
     whole, whether or not arising from transactions in the ordinary course of
     business, except as set forth in or contemplated by such documents.

     (k) Thermo Electron shall have furnished to the Representatives a
certificate of the Company, signed by the Chairman of the Board, Chief Executive
Officer, the President or a Vice President and the Treasurer, Secretary or an
Assistant Secretary of Thermo Electron, dated the Closing Date, to the effect
that the signers of such certificate have carefully examined the Registration
Statement, the Prospectus, any supplements to the Prospectus and this Agreement
and that, to the best of such person's knowledge:

 
                                      -23-

               (i) the representations and warranties of Thermo Electron in this
     Agreement are true and correct on and as of the date of the certificate
     with the same effect as if made on the date of the certificate, and Thermo
     Electron has complied with all the agreements and satisfied all the
     conditions on its part to be performed or satisfied at or prior to the
     Closing Date;

               (ii) no stop order suspending the effectiveness of the
     Registration Statement has been issued and no proceedings for that purpose
     have been instituted or, to such person's knowledge, threatened; and

               (iii)  since the respective dates as of which information is
     given in the Registration Statement, the Base Prospectus and any
     Preliminary  Prospectus as in effect at the time of execution of the
     applicable Terms Agreement, there has been no material adverse change in
     the consolidated financial condition, stockholders' equity, results of
     operations or business of Thermo Electron and its Subsidiaries taken as a
     whole, whether or not arising from transactions in the ordinary course of
     business, except as set forth in or contemplated by such documents.

          (l)  (i)  Neither the Company, Thermo Electron, nor any of their
respective Subsidiaries shall have sustained since the respective dates as of
which information is given in the Registration Statement, the Base Prospectus
and any Preliminary Prospectus as in effect at the time of execution of the
applicable Terms Agreement, any loss or interference with its business from
fire, explosion, flood or other calamity, whether or not covered by insurance,
or from any labor dispute or court or governmental action, order or decree,
which is material to the Company and its Subsidiaries taken as a whole, or
material to Thermo Electron and its Subsidiaries taken as a whole, as the case
may be, otherwise than as set forth in or contemplated by such documents, or

               (ii) since the date of the most recent financial statements of
the Company and Thermo Electron, as the case may be, contained in the
Registration Statement, the Base Prospectus and any Preliminary Prospectus as in
effect at the time of execution of the applicable Terms Agreement, there shall
not have been any change in the capital stock or consolidated long-term debt of
the Company or Thermo Electron, except as set forth in the letters described in
paragraphs (g) or (h) of this Section 7, or any material adverse change in the
general affairs, operations, business, prospects, key personnel, capitalization,
financial condition, shareholders' equity or results of operations of the
Company and its Subsidiaries taken as a whole, or of Thermo Electron and its
Subsidiaries taken as a whole, otherwise than as set forth in or contemplated by
the Registration Statement, the Base Prospectus and any Preliminary Prospectus
as in effect at the time of execution of the applicable Terms Agreement, the
effect of which, in any such case described in clause (i) or (ii), is, in the
judgment of the Representatives or a majority in interest of the Underwriters,
so material and adverse as to make it impracticable or inadvisable to proceed
with the public offering or the delivery of the Offered Securities being
delivered on such Closing Date on the terms and in the manner contemplated in
the Prospectus.

 
                                      -24-


          (m)  Subsequent to the execution and delivery of this Agreement and
prior to the Closing Date, (i) no downgrading shall have occurred in the rating
accorded Thermo Electron's or the Company's securities by any "nationally
recognized statistical rating organization", as that term is defined by the
Commission for purposes of Rule 436(g)(2) of the Rules and Regulations and (ii)
no such organization shall have publicly announced that it has under
surveillance or review, with possible negative implications, its rating of any
of Thermo Electron's or the Company's securities.

          (n)  Subsequent to the execution and delivery of this Agreement there
shall not have occurred any of the following:

               (i) trading in securities generally on the New York Stock
Exchange, the American Stock Exchange, the NASDAQ National Market or in the
over-the-counter market, or trading in any securities of the Company or Thermo
Electron on any exchange or in the over-the-counter market, shall have been
suspended or minimum prices shall have been established on any such exchange or
such market by the Commission, by such exchange or by any other regulatory body
or governmental authority having jurisdiction,

               (ii) a general banking moratorium shall have been declared by
federal or New York state authorities;

               (iii) the United States shall have become engaged in hostilities,
there shall have been an escalation in hostilities involving the United States
or there shall have been a declaration of a national emergency or war by the
United States; or

               (iv) there shall have occurred such a material adverse change in
general economic or financial conditions (or such a material adverse change in
international conditions the effect of which on the financial markets in the
United States shall be such) as to make it, in the judgment of the
Representatives or a majority in interest of the several Underwriters,
impracticable or inadvisable to proceed with the public offering or delivery of
the Offered Securities being delivered on such Closing Date on the terms and in
the manner contemplated in the Prospectus.

     All opinions, letters, evidence and certificates mentioned above or
elsewhere in this Agreement shall be deemed to be in compliance with the
provisions hereof only if they are in substance reasonably satisfactory to
counsel for the Underwriters.  The Company and Thermo Electron may rely on any
waiver of such conditions given by the Underwriters or counsel to the
Underwriters as if given by the Underwriters.

     8.   Indemnification and Contribution. (a) The Company and Thermo Electron,
          --------------------------------                                      
jointly and severally, shall indemnify and hold harmless each Underwriter, its
officers and employees and each such person, if any, who controls any
Underwriter, within the meaning of the Securities Act, from and against any and
all loss, claim, damage or liability, joint or several, or any action in respect
thereof (including, but not limited to any losses, claims, damages, liabilities
or actions relating to purchases and sales of the Offered Securities), to which
that Underwriter, officer,

 
                                      -25-

employee or controlling person may become subject, under the Securities Act or
otherwise, insofar as such loss, claim, damage, liability or action arises out
of, or is based upon,

          (i)  any untrue statement or alleged untrue statement made by the
Company or Thermo Electron in Section 1 hereof ; or

          (ii) any untrue statement or alleged untrue statement of a material
fact contained in any Preliminary Prospectus, the Registration Statement or the
Prospectus or in any amendment or supplement thereto; or

          (iii)  the omission or alleged omission to state in any Preliminary
Prospectus, the Registration Statement or the Prospectus, or in any amendment or
supplement thereto, any material fact required to be stated therein or necessary
to make the statements therein (in the case of the Prospectus or any Preliminary
Prospectus, in light of the circumstances in which they were made) not
misleading; or

          (iv)  any act or failure to act or any alleged act or failure to act
by any Underwriter in connection with, or relating in any manner to, the Offered
Securities or the offering contemplated hereby, and which is included as part of
or referred to in any loss, claim, damage, liability or action arising out of or
based upon matters covered by clause (ii) or (iii) above (provided that the
Company and Thermo Electron shall not be liable under this clause (iv) to the
extent that it is determined in a final judgment by a court of competent
jurisdiction that such loss, claim, damage, liability or action resulted
directly or indirectly from any such acts or failures to act undertaken or
omitted to be taken by such Underwriter through its gross negligence or willful
misconduct or breach of this Agreement); and shall reimburse each Underwriter
and each such officer, employee or controlling person within 30 days after
receiving written demand therefor for any legal or other expenses reasonably
incurred by that Underwriter, officer, employee or controlling person in
connection with investigating or defending or preparing to defend against any
such loss, claim, damage, liability or action; provided, however, that the
Company and Thermo Electron shall not be liable in any such case to the extent
that any such loss, claim, damage, liability or action arises out of, or is
based upon, any untrue statement or alleged untrue statement or omission or
alleged omission in any Preliminary Prospectus, the Registration Statement or
the Prospectus, or in any such amendment or supplement in reliance upon and in
conformity with written information concerning such Underwriter furnished to the
Company through any Underwriter by or on behalf of any Underwriter specifically
for inclusion therein; and provided, further, that the Company and Thermo
Electron shall not be liable to any Underwriter under the indemnity agreement in
this subsection with respect to any Preliminary Prospectus to the extent that
any such loss, claim, damage, liability or any action in respect thereof of such
Underwriter results from the fact that such Underwriter sold Offered Securities
to a person as to whom it shall be established that there was not sent or given,
at or prior to the written confirmation of such sale, a copy of the Prospectus
or of the Prospectus as then amended or supplemented in any case where such
delivery is required by the Securities Act if the Company has previously
furnished copies thereof in sufficient quantity to such Underwriter and the
loss, claim, damage or liability of such


 
                                      -26-

Underwriter results from an untrue statement or omission of a material fact
contained in the Preliminary Prospectus which was (i) identified to such
Underwriter at or prior to the earlier of the filing with the Commission or the
furnishing to such Underwriter of the Prospectus and (ii) corrected in the
Prospectus or in the Prospectus as then amended or supplemented. The foregoing
indemnity agreement is in addition to any liability which the Company or Thermo
Electron may otherwise have to any Underwriter or to any officer, employee or
controlling person of that Underwriter.

     (b) Each Underwriter, severally and not jointly, shall indemnify and hold
harmless the Company and Thermo Electron and their respective officers and
employees, each of their respective directors, and each person, if any, who
controls the Company or Thermo Electron within the meaning of the Securities
Act, from and against any loss, claim, damage or liability, joint or several, or
any action in respect thereof (including, but not limited to, any losses,
claims, damages, liabilities or actions relating to the purchases and sales of
Offered Securities), to which the Company or Thermo Electron or any such
director, officer or controlling person may become subject, under the Securities
Act or otherwise, insofar as such loss, claim, damage, liability or action
arises out of, or is based upon,

          (i) any untrue statement or alleged untrue statement of a material
fact contained in any Preliminary Prospectus, the Registration Statement or the
Prospectus or in any amendment or supplement thereto or

          (ii) the omission or alleged omission to state in any Preliminary
Prospectus, the Registration Statement or the Prospectus, or in any amendment or
supplement thereto, any material fact required to be stated therein or necessary
to make the statements therein not misleading, but in each case only to the
extent that the untrue statement or alleged untrue statement or omission or
alleged omission was made in reliance upon and in conformity with written
information concerning such Underwriter furnished to the Company through the
Underwriters by or on behalf of that Underwriter specifically for inclusion
therein, and shall reimburse, within 30 days after receiving written demand
therefor, the Company, Thermo Electron and any such director, officer or
controlling person for any legal or other expenses reasonably incurred by the
Company, Thermo Electron or any such director, officer or controlling person in
connection with investigating or defending or preparing to defend against any
such loss, claim, damage, liability or action.  The foregoing indemnity
agreement is in addition to any liability which any Underwriter may otherwise
have to the Company or Thermo Electron or any such director, officer, employee
or controlling person.

     (c) Promptly after receipt by an indemnified party under this Section 8 of
notice of any claim or the commencement of any action, the indemnified party
shall, if a claim in respect thereof is to be made against the indemnifying
party under this Section 8, notify the indemnifying party in writing of the
claim or the commencement of that action; provided, however, that the failure to
notify the indemnifying party shall not relieve it from any liability which it
may have under this Section 8 except to the extent it has been materially
prejudiced by such failure and, provided further, that the failure to notify the
indemnifying party shall not relieve it from any liability which it may have to
an indemnified party otherwise than under

 
                                      -27-

Section 8 (a) or (b). If any such claim or action shall be brought against an
indemnified party, and it shall notify the indemnifying party thereof, the
indemnifying party shall be entitled to participate therein and, to the extent
that it wishes, jointly with any other similarly notified indemnifying party, to
assume the defense thereof with counsel reasonably satisfactory to the
indemnified party. After notice from the indemnifying party to the indemnified
party of its election to assume the defense of such claim or action, the
indemnifying party shall not be liable to the indemnified party under this
Section 8 for any legal or other expenses subsequently incurred by the
indemnified party in connection with the defense thereof other than reasonable
costs of investigation; provided that the Representatives shall have the right
to employ counsel to represent you and those other Underwriters who may be
subject to liability arising out of any claim in respect of which indemnity may
be sought by the Underwriters against the Company or Thermo Electron hereunder
if, in your reasonable judgment, it is advisable for you and those Underwriters
to be represented by separate counsel, and in that event the fees and expenses
of such separate counsel shall be paid by the indemnifying party or parties, and
provided, further, in no event, shall the indemnifying party or parties be
responsible for the expenses of more than one separate counsel for all such
indemnified parties.

     No indemnifying party shall (i) without the prior written consent of the
indemnified parties (which consent shall not be unreasonably withheld), settle
or compromise or consent to the entry of any judgment with respect to any
pending or threatened claim, action, suit or proceeding in respect of which
indemnification or contribution may be sought hereunder (whether or not the
indemnified parties are actual or potential parties to such claim or action)
unless such settlement, compromise, consent or judgment (A) includes an
unconditional release of each indemnified party from all liability arising out
of such claim, action, suit or proceeding, and (B) does not include a statement
as to or an admission of fault, culpability or failure to act by or on behalf of
any indemnified party, or (ii) be liable for any settlement of any such action
effected without its written consent, but if settled with the consent of the
indemnifying party or if there be a final judgment for the plaintiff in any such
action, the indemnifying party agrees to indemnify and hold harmless any
indemnified party from and against any loss or liability by reason of such
settlement or judgment.

     (d) If the indemnification provided for in this Section 8 shall for any
reason be unavailable to or insufficient to hold harmless an indemnified party
under Section 8(a) or 8(b) in respect of any loss, claim, damage or liability,
or any action in respect thereof, referred to therein, then each indemnifying
party shall, in lieu of indemnifying such indemnified party, contribute to the
amount paid or payable by such indemnified party as a result of such loss,
claim, damage or liability, or action in respect thereof,

          (i) in such proportion as shall be appropriate to reflect the relative
benefits received  by the Company and Thermo Electron on the one hand and the
Underwriters on the other from the offering of the Offered Securities or

          (ii) if the allocation provided by clause (i) above is not permitted
by applicable law, in such proportion as is appropriate to reflect not only the
relative benefits referred to in clause (i) above but also the fault of the
Company and Thermo Electron on the one

 
                                      -28-

hand and the Underwriters on the other with respect to the statements or
omissions which in such loss, claim, damage or liability, or action in respect
thereof, as well as any other relevant equitable considerations. The relative
benefits received by the Company and Thermo Electron on the one hand and the
Underwriters on the other with respect to such offering shall be deemed to be in
the same proportion as the total net proceeds from the offering of the Offered
Securities purchased under this Agreement (before deducting expenses) received
by the Company on the one hand, and the total underwriting discounts and
commissions received by the Underwriters with respect to the Offered Securities
purchased under this Agreement, on the other, bear to the total gross proceeds
from the offering of the Offered Securities under this Agreement in each case as
set forth in the table on the cover page of the Prospectus. The relative fault
shall be determined by reference to whether the untrue or alleged untrue
statement of a material fact or omission or alleged omission to state a material
fact relates to information supplied by the Company or Thermo Electron, on the
one hand, or the Underwriters on the other, the intent of the parties and their
relative knowledge, access to information and opportunity to correct or prevent
such statement or omission. The Company, Thermo Electron and the Underwriters
agree that it would not be just and equitable if contributions pursuant to this
Section were to be determined by pro rata allocation (even if the Underwriters
were treated as one entity for such purpose) or by any other method of
allocation which does not take into account the equitable considerations
referred to herein. The amount paid or payable by an indemnified party as a
result of the loss, claim, damage or liability, or action in respect thereof,
referred to above in this Section 8 shall be deemed to include, for purposes of
this Section 8(d), any legal or other expenses reasonably incurred by such
indemnified party in connection with investigating or defending any such action
or claim. Notwithstanding the provisions of this Section 8(d), no Underwriter
shall be required to contribute any amount in excess of the amount by which the
total price at which the Offered Securities underwritten by it and distributed
to the public was offered to the public exceeds the amount of any damages which
such Underwriter has otherwise paid or become liable to pay by reason of any
untrue or alleged untrue statement or omission or alleged omission. No person
guilty of fraudulent misrepresentation (within the meaning of Section 11(f) of
the Securities Act) shall be entitled to contribution from any person who was
not guilty of such fraudulent misrepresentation. The Underwriters' obligations
to contribute as provided in this Section 8(d) are several in proportion to
their respective underwriting obligations and not joint. The provisions of this
Section 8(d) shall be applied separately to each offering of Offered Securities.

     (e) The Underwriters severally confirm that the following statements are
correct and constitute information concerning such Underwriters furnished in
writing to the Company by or on behalf of the Underwriters specifically for
inclusion in the Registration Statement and the Prospectus: (i) the legend in
the Prospectus concerning stabilization and over-allotment by the Underwriters,
(ii) the statements with respect to the public offering of the Offered
Securities by the Underwriters set forth on the cover page of the Prospectus and
(iii) the statements  concerning concessions, allowances and reallowances and
stabilization and over-allotment set forth under the caption "Underwriting" in
the Prospectus.

     9.    Defaulting Underwriters.  If on the applicable Closing Date, any
           -----------------------                                         
Underwriter defaults in the performance of its obligations under this Agreement,
the remaining non-defaulting Underwriters shall be obligated to purchase (in
addition to the amount of Offered Securities

 
                                      -29-

which such Underwriters are obligated to purchase pursuant to Section 2) the
Offered Securities which the defaulting Underwriter agreed but failed to
purchase on such Closing Date in the respective proportions to the amount of
Offered Securities set opposite the names of each remaining non-defaulting
Underwriter in Exhibit A to the applicable Terms Agreement bears to the amount
               ---------       
of the Offered Securities set opposite the names of all the remaining non-
defaulting Underwriters in Exhibit A to the applicable Terms Agreement;
                           ---------       
provided, however, that the remaining non-defaulting Underwriters shall not be
obligated to purchase any of the Offered Securities on such Closing Date if the
total number of Offered Securities which the defaulting Underwriter or
Underwriters agreed but failed to purchase on such date exceeds 10% of the total
amount of the Offered Securities to be purchased on such Closing Date. If the
foregoing maximum percentage is exceeded, the remaining non-defaulting
Underwriters, or those other underwriters satisfactory to the Underwriters who
so agree, shall have the right, but shall not be obligated, to purchase, in such
proportion as may be agreed upon among them, all the Offered Securities to be
purchased on such Closing Date. If the non-defaulting Underwriters or the other
underwriters satisfactory to the Underwriters do not elect to purchase the
Offered Securities which the defaulting Underwriter or Underwriters agreed but
failed to purchase, this Agreement shall. terminate without liability on the
part of any non-defaulting Underwriter or the Company or Thermo Electron, except
that the Company, Thermo Electron and the Underwriters will continue to be
liable for the payment of expenses to the extent set forth in Sections 6 and 11
and continue to be liable under Section 8. As used in this Agreement, the term
"Underwriter" includes, for all purposes of this Agreement unless the context
 -----------           
requires otherwise, any party not listed in Exhibit A to any applicable Terms
                                            ---------
Agreement who, pursuant to this Section 9, purchases Offered Securities which a
defaulting Underwriter agreed but failed to purchase. Nothing contained herein
shall relieve a defaulting Underwriter of any liability it may have to the
Company for damages caused by its default. If other underwriters are obligated
or agree to purchase the Offered Securities of a defaulting or withdrawing
Underwriter, either the Underwriters or the Company may postpone the applicable
Closing Date for up to seven full business days in order to effect any changes
that in the reasonable opinion of counsel for the Company or counsel for the
Underwriters may be necessary in the Registration Statement, the Prospectus or
in any other document or arrangement necessary to consummate the transactions
described herein.

     10.  Termination.  The obligations of the Underwriters under this Agreement
          -----------                                                           
may be terminated by the Representatives or by Underwriters which have agreed to
purchase in the aggregate 50% or more of the aggregate amount of Offered
Securities by notice given to and received by the Company prior to delivery of
and payment for the Offered Securities if, prior to that time, any of the events
described in Sections 7(i), (l), (m) or (n) (but as to subsection (m) only, only
if the offering is of Debt Securities) shall have occurred or if the
Underwriters shall decline to purchase the Offered Securities for any reason
permitted under this Agreement.

     11.  Reimbursement of Underwriters' Expenses.  If the Company shall fail to
          ---------------------------------------                               
tender the Offered Securities for delivery to the Underwriters by reason of any
failure, refusal or inability on the part of the Company or Thermo Electron to
perform any agreement on its part to be performed, or because any other
condition of the Underwriters' obligations hereunder required to be fulfilled by
the Company or Thermo Electron is not fulfilled, the Company will reimburse

 
                                      -30-

the Underwriters for all reasonable out-of-pocket expenses (including fees and
disbursements of counsel) incurred by the Underwriters in connection with this
Agreement and the proposed purchase of the Offered Securities, and upon demand
the Company shall pay the full amount thereof to the Underwriters. If this
Agreement is terminated pursuant to Section 9 by reason of the default of one or
more Underwriters, the Company shall not be obligated to reimburse any
defaulting Underwriter for any of its expenses incurred in connection with this
Agreement.

     12.  Notices, etc.  All statements, requests, notices and agreements
          ------------                                                   
hereunder shall be in writing, and:

          (a) if to the Underwriters, shall be delivered or sent by mail, telex
or facsimile transmission, if Lehman Brothers Inc. is one of the Underwriters,
c/o Lehman Brothers Inc., Three World Financial Center, New York, New York
10285, Attention: Syndicate Department (Fax: 212-526-6588), with a copy, in the
case of any notice pursuant to Section 8(c), to the Director of Litigation,
Office of the General Counsel, Lehman Brothers Inc., World Financial Center,
10th Floor, New York, NY 10285, if Goldman, Sachs & Co. is one of the
Underwriters, c/o Goldman, Sachs & Co., 85 Broad Street, New York, NY 10004,
Attention:  Registration Department (Fax:  212-357-0926) and if Smith Barney
Inc. is one of the Underwriters, c/o Seven World Trade Center, New York, NY
10048 (Fax:  212-783-4548; and

          (b) if to the Company or Thermo Electron, shall be delivered or sent
by mail, telex or facsimile transmission to the address of the Company or Thermo
Electron set forth in the Registration Statement, Attention: General Counsel
(Fax: (617) 622-1283).

Any such statements, requests, notices or agreements shall take effect at the
time of receipt thereof.  The Company and Thermo Electron shall be entitled to
act and rely upon any request, consent, notice or agreement given or made on
behalf of the Underwriters by the Representatives.

     13.  Persons Entitled to Benefit of Agreement.  This Agreement shall inure
          ----------------------------------------                             
to the benefit of and be binding upon the Underwriters, the Company and Thermo
Electron and their respective successors.  This Agreement  and the terms and
provisions hereof are for the sole benefit of only those persons, except that
(A) the representations, warranties, indemnities and agreements of the Company
and Thermo Electron contained in this Agreement shall also be deemed to be for
the benefit of the person or persons, if any, who control any Underwriter within
the meaning of Section 15 of the Securities Act and (B) the indemnity agreement
of the Underwriters contained in Section 8(b) of this Agreement shall be deemed
to be for the benefit of the directors of the Company and Thermo Electron,
officers of the Company and Thermo Electron and any person controlling the
Company or Thermo Electron within the meaning of Section 15 of the Securities
Act.  Nothing in this Agreement is intended or shall be construed to give any
person, other than the persons referred to in this Section 13, any legal or
equitable right, remedy or claim under or in respect of this Agreement or any
provision contained herein.

     14.  Survival.  The respective indemnities, representations, warranties and
          --------                                                              
agreements of the Company, Thermo Electron and the Underwriters contained in
this Agreement or made by

 
                                      -31-

or on behalf of them, respectively, pursuant to this Agreement, shall survive
the delivery of and payment for any Offered Securities and shall remain in full
force and effect, regardless of any investigation made by or on behalf of any of
them or any person controlling any of them.

     15.  Definition of the Terms "Business Day," "Significant Subsidiary" and
          --------------------------------------------------------------------
"Subsidiary."   For purposes of this Agreement, (a) "business day" means any day
- -----------                                          ------------               
on which the New York Stock Exchange, Inc. is open for trading, (b) "Subsidiary"
                                                                     ---------- 
has the meaning set forth in Rule 405 of the Rules and Regulations and (c)
                                                                          
"Significant Subsidiary" has the meaning set forth in Item 1-02(w) of the
- -----------------------                                                  
Regulation S-X of the Rules and Regulations.

     16.  Performance by the Company.  Thermo Electron agrees to cause the
          --------------------------                                      
Company to perform each of the agreements and obligations of the Company
contained in this Agreement.

     17.  Governing Law.  This Agreement shall be governed by and construed in
          -------------                                                       
accordance with the laws of Massachusetts.

     18.  Counterparts.  This Agreement may be executed in counterparts and, if
          ------------                                                         
executed in more than one counterpart, the executed counterparts shall each be
deemed to be an original but all such counterparts shall together constitute one
and the same instrument.

     19.  Headings.  The headings herein are inserted for convenience of
          --------                                                      
reference only and are not intended to be part of, or to affect the meaning or
interpretation of, this Agreement.



                  [Remainder of page intentionally left blank]

 
                                      -32-



     If the foregoing correctly sets forth the agreement between the Company,
Thermo Electron and the Underwriters, please indicate your acceptance in the
space provided for that purpose below.

                              Very truly yours,

                              Thermo Instrument Systems Inc.

                              By: /s/ Melissa F. Riordan
                                  _________________________
                                  Name:  Melissa F. Riordan
                                  Title: Treasurer
 
 
                              Thermo Electron Corporation

                              By: /s/ Melissa F. Riordan
                                  _________________________
                                  Name:  Melissa F. Riordan
                                  Title: Treasurer

Accepted:

Lehman Brothers Inc.
Goldman, Sachs & Co.
Smith Barney Inc.

By: Lehman Brothers Inc.

By: /s/ Kevin Davies
    ____________________________________
    Name:  Kevin Davies
    Title: Associate, Investment Banking

 
 
                                                                      SCHEDULE I

                                TERMS AGREEMENT


                                                January __, 1998

To each of the Underwriters
named on Exhibit A hereto

Dear Sirs:

       Thermo Instrument Systems Inc., a Delaware corporation (the "Company"),
                                                                    -------   
proposes to issue and sell $___ million aggregate principal amount of its debt
securities with the terms set forth below (the "Offered Securities").  Subject
                                                ------------------            
to the terms and conditions set forth herein or incorporated by reference
herein, the underwriters named on Exhibit A hereto (the "Underwriters") offer to
                                  ---------              ------------           
purchase, severally and not jointly, the principal amount of Offered Securities
set forth therein opposite their respective names at __% of the principal amount
thereof.  

     The Offered Securities shall have the following terms:

     Title: ___% Convertible Subordinated Debentures due 200_

     Maturity:

     Interest rate: ___% per annum

     Interest payment dates:  ___ and ______, commencing ____, 199_

     Redemption provisions:  Redeemable at the option of the Company, in whole
     or in part, at any time on or after ____________ at 100% of the principal
     amount thereof, together with accrued interest to the date of redemption.

     Repayment provisions:  Subject to repayment at the option of the holder at
     100% of the principal amount thereof, together with accrued interest to the
     date of repayment, in the event the Common Stock is neither listed for
     trading on a United States national securities exchange, Nasdaq National
     Market nor approved for trading on an established automated over-the-
     counter trading market in the United States.


                                                                       Exhibit A
                                      -2-

     Conversion provisions: Convertible at any time (except that Offered
     Securities issued in bearer form will not be convertible until the date 40
     days after the Closing Date) into shares of Common Stock of the Company at
     an initial conversion price of $____.

     Guarantee:  Guaranteed on a subordinated basis by Thermo Electron
     Corporation.

     Form:    To be issued in registered form and bearer form.  The Offered
     Securities issued in bearer form will be initially represented by a
     temporary global bearer Offered Security exchangeable for definitive
     Offered Securities commencing on the date 40 days after the Closing Date.

     The Closing Date shall be January __, 1998.

     All the provisions contained in the Underwriting Agreement dated January
__, 1998 among Lehman Brothers Inc., Goldman, Sachs & Co., Smith Barney Inc.,
the Company and Thermo Electron Corporation, and in the Joint Officers'
Certificate dated January __, 1998, executed by the Company and Thermo Electron,
copies of which you have previously received, are herein incorporated by
reference (except for provisions that relate to securities other than Offered
Securities designated herein) in their entirety and shall be deemed to be a part
of this Terms Agreement to the same extent as if such provisions had been set
forth in full herein.  Terms defined in the Underwriting Agreement are used
herein as therein defined.

     The Company agrees to be bound by the provisions of Section 5(i) of the
Underwriting Agreement.

     Payment for the Offered Securities shall be made to or upon the order of
the Company on the Closing Date by wire transfer in immediately available funds.


                  REMAINDER OF PAGE INTENTIONALLY LEFT BLANK


 
                                      -3-

     Please accept this offer by signing a copy of this Terms Agreement in the
space set forth below.

                                                 Very truly yours,

Accepted on January __, 1998                     THERMO INSTRUMENT SYSTEMS INC.

LEHMAN BROTHERS INC.
GOLDMAN, SACHS & CO.                             By:___________________________
SMITH BARNEY INC.                                Name:
                                                   Title:

By:  LEHMAN BROTHERS INC.                        THERMO ELECTRON CORPORATION

 
By: ____________________                         By:___________________________
    Name:                                           Name:
    Title:                                          Title:


 
  EXHIBIT A
  ---------

  LIST OF UNDERWRITERS
 
 
 
 
                                                           Principal Amount
Underwriter                                                 of Debentures
- -----------                                                ----------------

                                                            
Lehman Brothers Inc......................................
Goldman, Sachs & Co......................................
Smith Barney Inc.........................................
                                      Total..............