<PAGE>
 
                                                                   EXHIBIT 10.11

                              INDENTURE OF LEASE
                              ------------------


                            (Dated - July 15, 1997)


                                   Premises
                                   --------


                 (60 Fordham Road, Wilmington, Massachusetts)


        (Executed in Four (4) Counterparts; with Signatures on page 53;
              and pages initialed, as set forth in Section 8.26)


                              (Table of Contents)
--------------------------------------------------------------------------------

A.   PARTIES:-
     -------- 


     1.    LESSOR: - THE WILMINGTON REALTY TRUST
     2.    LESSEE: - GENERAL SCANNING, INC.


B.   PREMISES:
     -------- 

     1.    The LEASED PREMISES, including land, building, parking area, rights
           of access, etc., are shown on two (2) Plans (FOR LAND IN WILMINGTON,
           MA. PREPARED FOR WILMINGTON REALTY TRUST) attached to, and
           incorporated in, the INDENTURE OF LEASE; both Plans prepared by
           Martinage Engineering Associates, Inc.; --both dated September 18,
           1997, as follows

          a.  EXHIBIT A - entitled "EXHIBIT A - TO ACCOMPANY LEASE AGREEMENT"
          b.  EXHIBIT B - entitled "EXHIBIT B - FUTURE LAYOUT PLAN"
          c.  EXHIBIT C - Agreement dated May 19, 1997


     2.   Area of the LEASED PREMISES:

          a.  Land (as shown on said EXHIBIT A) -  11.6355 acres - more or less;
          b.  Building

             (a)  Address - 60 Fordham Road, Wilmington, Mass. 01887 (Building
                  No.2)
             (b)  Square footage of Building (agreed) - 78,180 square feet

C.   TERM: - Ten (10) years, with two (2) successive five (5) year options.
     ----                                                                  

D.   COMMENCEMENT DATE:  December 1, 1997
     -----------------                   

--------------------------------------------------------------------------------
<PAGE>
 
 
                               TABLE OF CONTENTS
                               -----------------

                             ARTICLES and SECTIONS

                                       of

                              INDENTURE OF LEASE
                            (Dated - July 15, 1997)

                      (IN FIVE SHEETS-PAGES I THROUGH V)

<TABLE>
<CAPTION>
ARTICLE and SECTION                                                                                       PAR 
-------     -------                                              
<S>                                                                                                       <C> 
ARTICLE I -- SALIENT COVENANTS and REFERENCE DATA                                                          1                      
             ------------------------------------

1.11      AGREEMENT TO IMPROVE AND LEASE PREMISES                                                          1                      
1.2       THE PARTIES                                                                                      2                      
          1.2.1 LESSOR                                                                                     2                      
          1.2.2 LESSEE                                                                                     2                      
1.3       COMMENCEMENT DATE                                                                                3                      
1.4       ORIGINAL TERM                                                                                    3                      
1.5       THE LEASED PREMISES                                                                              3                      
1.6       ANNUAL FIXED RENT                                                                                5                      
          1.6.1 FORMULA                                                                                    5                      
          1.6.2 ANNUAL AND MONTHLY RENT                                                                    5                      
1.7       REAL ESTATE TAXES; MAINTENANCE, OPERATING EXPENSES                                               6                      
          1.7.1 MAINTENANCE                                                                                6                      
          1.7.2 TAXES                                                                                      7                      
          1.7.3 INSURANCE AND INDEMNIFICATION                                                              7                      
1.8       LESSEE'S UTILITIES                                                                               9                      
1.9       POSSIBLE EXPANSION                                                                               9                      
1.10      OPTION TO EXTEND LEASE                                                                           11 
1.11      SUBLEASING (Subject to the provisions of Section 5.6 through Section 5.6.6)                      12 
1.12      ENVIRONMENTAL - 21E, ETC. (G.E. - Lockheed)                                                      12 
1.13      EASEMENTS AND RIGHTS OF ACCESS (to Lessor, to Lockheed, to Ametek)                               14 
1.14      WASTE WATER TREATMENT PLANT                                                                      14 
1.15      PERMITTED USES                                                                                   16 
1.16      INITIAL MINIMAL LIMITS OF LESSEE'S GENERAL LIABILITY INSURANCE                                   16 
1.17      RECOGNIZED BROKERS                                                                               16 
1.18      EXHIBITS                                                                                         16 
           EXHIBIT A - Plan to Accompany Lease Agreement;                                                                       
           EXHIBIT B - Future Layout Plan                                                                                       
           EXHIBIT C - Agreement dated May 19, 1997                                                                             
 
ARTICLE II- THE BUILDINGS, PREMISES, TERM AND RENT                                                         16
            -------------------------------------- 

2.1       The Premises                                                                                     16
</TABLE>

                                       ii
<PAGE>
 
<TABLE> 
<S>                                                                         <C> 
2.2   Right to Use Common Facilities                                        17
      2.2.1   Lessee's Parking                                              18 
2.3   Landlord's Reservations (repairs, etc.)                               18
2.4   Habendum                                                              19
2.5   Monthly Fixed Rent Payments                                           19
2.6   Lessee Responsible For Maintenance, Etc.                              20
2.7   Real Estate Taxes; Payment:                                           20
      2.7.1   Tax Abatement - Procedure                                     21
2.8   Lessee's Electricity and Utilities.                                   22
                                                                             
ARTICLE III-CONDITION OF PREMISES                                           22
            ---------------------                                            
                                                                             
3.1   Delivery of Premises                                                  22
3.2   alterations and additions                                             22
3.3   General Provisions Applicable to Construction                         23
                                                                             
ARTICLE IV-COVENANTS OF THE LESSOR                                          23
           -----------------------                                           
                                                                             
4.1   LANDLORD'S COVENANTS                                                  23
                                                                             
      4.1.1   Delivery of Premises                                          23
      4.1.2   quiet enjoyment                                               23
      4.1.3   Structural Elements of the Exterior                           24
                                                                             
ARTICLE V-COVENANTS OF THE LESSEE                                           24
          -----------------------                                            
                                                                             
5.1   Payments                                                              24
5.2   Maintenance of the Premises Leased Hereunder;                           
      Yielding of Premises; Waste and Destruction                           24
5.3   Use and Occupancy of Leased Premises                                  25
                                                                             
      (A)  Prohibitions and Restrictions                                    25
      (B)  ENVIRONMENTAL CONTROL LAWS - Lessee shall comply with            25
      (C)  Light Manufacturing and Research and Development                 26
                                                                             
5.4   Obstructions; Items Visible from Exterior; Rules and Regulations      27
5.5   Safety Appliances; Licenses; Security Systems                         27
5.6   Assignment; Sublease (section 5.6 through section 5.6.6)              27
                                                                              
      5.6.1   Subsidiaries; Affiliated entities; Merger                     27
      5.6.2   Written Notice of Assignment under section 5.6.1              28
      5.6.3   No Assignment, Sublease or Subletting                         28
              Without Prior Written Consent of Lessor                       28
      5.6.4   Notice of Proposed Assignment, Subletting or Subleasing.      29
      5.6.5   Consent to Assignment Conditional upon                           
              Guarantee of the lessee (Payment of Rent, etc.)               29
      5.6.6   Responsibility in the Event of Assignment or Subleasing       30 
</TABLE>

                                      iii
<PAGE>
 
<TABLE>
<S>                                                                         <C> 
5.7   Indemnification; - Insurance                                          31
 
      (A)  Indemnification                                                  31
      (B)  INSURANCE                                                        31
 
5.8   Furnishings, etc. of Lessee at Lessee's Risk                          32
5.9   Right of Entry                                                        32
5.10  Floor Load; Prevention of Vibration and Noise                         33
5.11  Personal Property Taxes                                               33
5.12  Compliance with Laws                                                  33
5.13  Payment of Litigation Expenses                                        34
 
ARTICLE VI-CASUALTY AND TAKING                                              28
           -------------------

6.1   Fire and Casualty - Termination of Restoration: Rent Adjustment       34
 
      (A)  Restoration - Termination                                        34
      (B)  Damage during Last Year                                          34
      (C)  Rent Adjustment in the Event of Temporary Displacement           35
      (D)  Insurance Proceeds; Restoration                                  35
 
6.2   Loss Caused by Uninsured Risk                                         36
6.3   Condemnation - Taking by Right of Eminent Domain                      36
6.4   Awards Resulting from eminent domain Takings (Reserved)               37

ARTICLE VII-DEFAULT                                                         38
            -------

7.1   DEFAULT BY LESSEE                                                     38

      (A)  "Events of Default"                                              38
      (B)  In the Event of Occurrence of any said "Events of Default"
           by the Lessee                                                    39
      (C)  Entry by Lessor upon Such Termination                            39
      (D)  Responsibility of Lessee: Rent
      (E)  Liquidated Damages                                               40
      (F)  Rights of Lessor upon Entry after an "Event of Default"          40
      (G)  Remedies are Cumulative and not Exclusive upon Default           41
 
7.2   Default by the Lessor of its Obligations under this Lease             41

ARTICLE III-MISCELLANEOUS PROVISIONS                                        41
            ------------------------
 
8.1   Extra Hazardous Use                                                   42
8.2   Waiver                                                                42
8.3   Cumulative Remedies                                                   42
8.4   Quiet Enjoyment                                                       42
8.5   Notice to Mortgagee and Ground Landlord                               43
8.6   Assignment of Rents                                                   43
</TABLE> 

                                      iv
<PAGE>
 
<TABLE> 
<S>                                                                         <C> 
8.7   Surrender                                                             44
8.8   Brokerage                                                             44
8.9   Invalidity of Particular Provisions                                   44
8.10  Provisions Binding, Etc.                                              45
8.11  Recording                                                             45
8.12  Notices                                                               45
8.13  When Lease Becomes Binding                                            46
8.14  Section Headings                                                      46
8.15  Rights of Mortgagee                                                   46
8.16  Status Report                                                         47
8.17  Self-Help                                                             47
8.18  Holding Over                                                          48
8.19  Non-Subrogation                                                       48
8.20  Extension Option
 
      (A)  Conditions                                                       48
      (B)  First Five (5) Year Extended Term                                49
      (C)  Second Five (5) Year Extended Term                               49
      (D)  Option Granted to Extend for Two Five (5) year Terms Only        50
 
8.21  Lessee Shall Look Only to the Interest of the Lessor in the Premises 
      herein Leased                                                         51
8.21  The Trustees of Lessor and Beneficiaries Not Personally Liable        51
8.22  Late Payment                                                          51
8.23  Governing Law                                                         52
8.24  Indentures 53 pages (Eight Articles - Three Exhibits)                 52
8.25  This Lease Conditional upon Release of Premises by AMETEK             52
8.26  Counsel                                                               52
8.27  Dispute Resolution                                                    52
 
      Signatures                                                            53
      Exhibits Attached

               EXHIBIT A - Plan dated September 18, 1997 (Accompanying Lease)
               EXHIBIT B - Plan dated September 18, 1997 (Future Layout Plan)
               EXHIBIT C - Agreement dated May 19.1997 (14 pages)
</TABLE> 

 (Last of FIVE (5) PAGES OF TABLE OF CONTENTS TO INDENTURE OF LEASE DATED JULY
                                   15, 1997)
    (LESSOR: THE WILMINGTON REALTY TRUST;  LESSEE: GENERAL SCANNING, INC.)
     ------                                ------                         
        (PREMISES: - 60 FORDHAM ROAD, WILMINGTON, MASSACHUSETTS 01887)
         --------                                                     

                                       v
<PAGE>
 
                               INDENTURE OF LEASE
                                        


                                 in respect to



                     PREMISES in WILMINGTON, MASSACHUSETTS


     THIS INSTRUMENT, dated as of the 15th day of July, 1997, constitutes and
comprises an INDENTURE OF LEASE by and between THE WILMINGTON REALTY TRUST
(hereinafter generally referred to a the LESSOR) and GENERAL SCANNING, INC.
(hereinafter generally referred to as the LESSEE) - said parties hereinafter
more particularly defined and identified. This Indenture of Lease relates to
certain premises comprising a building with land, and parking areas (hereinafter
defined and shown on plans hereto annexed), and being a portion of the complex
located at, and numbered as, 50 Fordham Road, Wilmington, Massachusetts This
Indenture comprises ARTICLE I through ARTICLE VIII along with Exhibits attached
thereto


IN CONSIDERATION OF THE MUTUAL COVENANTS HEREIN SET FORTH, AND FOR VALUABLE
CONSIDERATION, THE PARTIES TO THIS INDENTURE OF LEASE DO HEREBY AND HEREWITH
PROMISE, COVENANT AND AGREE WITH EACH OTHER, AS FOLLOWS:


                                   ARTICLE I
                                   ------- -

                      SALIENT COVENANTS AND REFERENCE DATA
                      ------- ---------     --------- ----
                                        
The matters covered under ARTICLE I of this Indenture of Lease are, in some
instances, covered more extensively and in more detail in the remaining
ARTICLES. All portions of the lease shall be valid.

1.1. AGREEMENT dated May 19, 1997


     This indenture of Lease is entered into pursuant to an instrument dated May
     19, 1997 by and between the parties entitled "AGREEMENT to IMPROVE AND

                                       1
<PAGE>
 
     LEASE PREMISES" (EXHIBIT C); which Agreement is incorporated herein as an
     expression of the intent of the parties. However, in the event of any
     discrepancy between the provisions of this Indenture of Lease and said
     Agreement, the provisions of this Indenture shall prevail with respect to
     said discrepancy.



1.2  THE PARTIES:

1.2.1. LESSOR: The record owner and the lessor or of the premises herein leased
       is

       THE WILMINGTON REALTY TRUST; which Trust was established under a
       Declaration of Trust dated September 7, 1973; and which declaration is
       registered in the Middlesex South Registry District of the Land Court as
       Document No.15729, there noted on Certificate of Title No 142138; and
       registered, further, in the Middlesex North District of the Land Court as
       Document NO.63541, there noted on Certificate of Title 19837.

       The present Trustees of and under said Declaration of Trust are,
       respectively,

       ROSEMARIE STANIEICH, CLAUDIA J. CIPULLO and JOSEPH O. BRANZETTI, JR.,
       (which Trustee's have executed this Indenture for and on behalf of the
       said Lessor.)

       LESSOR'S ORIGINAL ADDRESS: -THE WILMINGTON REALTY TRUST
                                        
                  c/o Frank N. Dardeno, Jr. 424 Broadway
                  Somerville, Massachusetts 02145
                  (Present telephone No. (617) 666-2600

       LESSOR'S CONSTRUCTION REPRESENTATIVE: - FRANK M. BOMBA,

                  20 Lawndale Road
                  in Stoneham, Massachusetts 02180
                  (telephone no. (617) 438 3508)



1.2.2  LESSEE:

       GENERAL SCANNING INC., a corporation duly organized and existing under
       the laws of the Commonwealth of Massachusetts.

       LESSEE'S ORIGINAL ADDRESS: 500 Arsenal Street Watertown, 
                                  Massachusetts 02172

                                       2
<PAGE>
 
       LESSEE'S CONSTRUCTION REPRESENTATIVE: GEORGE HRONO,
                                    with a business address at 500 Arsenal
                                    Street, Watertown, Massachusetts 02172 and
                                    with a present telephone number (617) 924-
                                    1010, Extension 204

       The Lessor and the Lessee do both covenant and agree that this Indenture
       of Lease shall be binding upon each of them and upon the successors and
       assigns of each of them

1.3. COMMENCEMENT DATE:  December 1, 1997

1.4. ORIGINAL  TERM: The term of ten (10) years commencing on the Commencement
          Date (to wit: - December 1, 1997) and expiring on November 30, 2007
          unless extended or sooner terminated as hereinafter provided in this
          Indenture of Lease).

1.5. THE LEASED PREMISES:

   (A) The premises that are leased to the LESSEE under this Indenture are
       alternatively referred to, or identified as, the "Premises" or the "Site"
       or "the premises leased hereunder" or "the premises leased herein" or
       "the leased premises" or similar descriptive phraseology, as the context
       shall permit.

       The said premises leased hereunder comprise a portion of the land and
       buildings formerly occupied by GENERAL ELECTRIC COMPANY ("G.E.") under a
       lease dated November 13, 1969, as amended, and its successor, AMETEK
       AEROSPACE PRODUCTS, INC. ("AMETEK") Said Land and buildings, in their
       totality, are referred to herein as the "Complex" or as the "Facilities".

       The leased premises (the site) are a portion of those facilities situated
       in Wilmington and North Reading, Middlesex County, Massachusetts; located
       at, and numbered as, 50 Fordham Road, in Wilmington, Massachusetts

       Said site or leased premises comprise that one story building known as
       Building No.2 with parking area and all land pertaining thereto. Said
       Building No.2, parking area and land are located north of Building No.1
       and lA leased to AMETEK (said "AMETEK" building located in the southerly
       portion of the Complex).

   (B) The said leased premises or site are shown upon the plan entitled and
       attached hereto and incorporated herewith as Exhibit A

       The parties agree that the said leased premises (or site) are those shown
       upon said plan, as leased to "GENERAL SCANNING"

                                       3
<PAGE>
 
   (C) The parties have independently verified the floor space comprising said
       buildings, and the parties stipulate that the size of the floor space of
       said building is, and shall be, for the purposes of this lease, 78,180
       square feet.

       Said leased premises include the lot upon which said building was
       constructed and a portion of the parking area contiguous to the rear (or
       west) thereof; along with some open areas of land that may be appurtenant
       thereto.

       As aforesaid, the said leased premises area are shown upon a plan which
       shall be incorporated within, and be a part of; this Indenture of Lease
       to define and delineate the leased premises; said plan attached hereto
       as Exhibit A.

   (D) The title to the land upon which the Premises and the Facilities are
       located are registered in the Land Court of the Commonwealth of
       Massachusetts.

       The LESSOR reserves the right to lease the said premises and the land
       appurtenant thereto to the Lessee without formal approval of the plan
       delineating the said premises as a Subdivision.

       As set forth in the agreement of the parties in the above referred to
       AGREEMENT to IMPROVE and LEASE PREMISES, dated May 19, 1997, the Lessor
       reserves the right to transfer the title to the leased premises to a new
       Trust to establish a separate identity for the said leased premises.
       Further, the Lessor has, and shall have, the right to present, at any
       time, a plan delineating the leased premises as a Subdivision (under the
       Subdivision Control Law); including the designation of the premises as a
       condominium with participatory rights to the Waste Water Treatment
       Facility that services said premises.

       The LESSEE agrees that it shall execute promptly all documents and assent
       to all actions and do all things requested by the LESSOR of the LESSEE in
       order that the LESSOR may institute and complete any such transfer or
       subdivision or designation of and dedication to, such condominium
       ownership. The LESSEE shall assent thereto whether or not said transfer,
       or said subdivision, or said designation shall include the whole of the
       said Complex or Facilities or a portion thereof; and whether said action
       shall or shall not include the premises leased hereunder to the LESSEE.


  (E)  The premises hereunder leased to the LESSEE, and, particularly, the said
       building herein referred to as Building No.2, are expected to be
       designated under a new and separate post office address. Said premises
       and said building may, thereafter, be referred to or designated by or as
       said new and separate post office address. (The said address is 60
       Fordharn Road, said Wilmington.)

                                       4
<PAGE>
 
1.6.  ANNUAL FIXED RENT:

1.6.1  FORMULA

      In accordance with the "AGREEMENT to IMPROVE and LEASE PREMISES",
      aforesaid, dated May 19, 1997, and executed by the parties, the base
      annual rent during the initial ten (10) year term (commencing December 1,
      1997),- shall be calculated or determined on the basis of the square feet
      of floor space of said Building No.2; to wit.

      a.  Years one through three - at $5.00 per square foot (TRIPLE NET)
      b.  Years four through seven - at $5.40 per square foot (triple net)
      c.  Years eight through ten - at $5.80 per square foot (triple net)

      Said formula shall apply to the premises initially herein leased to the
      LESSEE and, particularly, Building No.2 in its present floor size.

      The parties stipulate, as aforesaid. that the square footage of said
      building, as presently built, comprises, 78,180 square feet.

1.6.2 ANNUAL and MONTHLY RENT:

      1.  During the period commencing December 1, 1997 and ending November 30,
          2000, the Lessee shall pay to the Lessor a base annual rent at the
          rate of three hundred ninety thousand, nine hundred and no/100
          ($390,900.00) dollars; said annual rent due and payable, in advance,
          in equal monthly payments of thirty two thousand, five hundred 
          seventy-five and no/100 ($32,575.00) dollars

      2.  During the period commencing December 1, 2000 and ending November 30,
          2004, the Lessee shall pay to the Lessor a base annual rent at the
          rate of four hundred twenty-two thousand, one hundred seventy-two and
          no/100 ($422,172.00) dollars; said annual rent due and payable, in
          advance, in equal monthly installments of thirty-five thousand, one
          hundred eighty-one and no/100 ($35,181.00) dollars.

      3.  During the period commencing December 1,2004 and ending November 30,
          2007, the Lessee shall pay to the Lessor a base annual rent at the
          rate of four hundred fifty-three thousand, four hundred forty-four and
          no/100 ($453,444.00) dollars; said annual rent due and payable, in
          advance, in equal monthly installments of thirty-seven thousand, seven
          hundred eighty-seven and no/100 ($37,787.00) dollars.

                                       5
<PAGE>
 
            All monthly installments of rent shall be due and payable on the
            first day of each month.

            As hereinafter provided, the base rent shall be increased to an
            amount to be agreed upon between the parties in the event there
            shall be constructed an addition to said Building No.2 and expansion
            of the floor space.

        4.  The above shall apply to the premises herein initially leased to the
            LESSEE with said Building No.2 in its present floor size. Therefore,
            the foregoing is subject to the provisions of Section 1.9 in the
            event of expansion as therein set forth.

        5.  Reference is herein made, also, to the provisions of Section 2.5 of
            this Indenture.

1.7.   REAL ESTATE TAXES; MAINTENANCE; OPERATING EXPENSES:

       Lessee shall pay all operating costs as and when due, including, without
       limitation,- all real estate and other taxes assessed against or with
       respect to the leased premises; any and all utilities; all insurance
       coverage (said insurance covering all risks, all liability against any
       loss occurring on or near said premises or as a result of any of the
       activities of the Lessee, any and all damages or loss caused by fire,
       storm or other insurable risks); ground care; snow removal; maintenance
       and service agreements for HVAC and for any other equipment or building
       elements; and all repairs and interior maintenance of the building and
       its appurtenances, as set forth in Section 1.7.1.

       Reference is herein made to the provisions set forth in Section 5.7 of
       this Indenture. As stipulated in said Section 5.7 (A) (a) (ii), the
       LESSEE shall, and does, indemnify and hold harmless the LESSOR against
       all losses and damages unless said losses or damages shall be caused by,
       or due to the fault of, the Lessor or tenants of the Lessor (other than
       the Lessee herein).

       Reference is here made to Section H. (RESPONSIBILITIES) of the Agreement
       of May 19, 1997.

1.7.1  Maintenance

       a.   Upon completion of all the renovations and improvements, the said
            building and its appurtenances will be in prime condition with new
            insulated roof; with structural replacements where needed, new
            mechanical elements, renovated and remodeled interior, new double
            pane glass throughout, paved parking area, etc.

                                       6
<PAGE>
 
     b.   All warrantees and guarantees issued by installers, contractors and
          suppliers shall be made available to the Lessee and shall be
          transferred to, or for the benefit of the Lessee..

     c.   The Lessee shall be responsible for all maintenance of the interior of
          the building, paved areas, mechanical appurtenances, all roofing
          elements, HVAC units, and all other aspects of the building and its
          facilities.

     d.   The lease shall be a triple net lease.

     e.   Not in limitation of the foregoing (and unless revised by prior
          written stipulation or agreement of the parties), the Lessee shall be
          responsible for all interior elements of the building, including its
          mechanical components, all wiring (electrical or otherwise), all
          plumbing , all surfaces, flooring and any and all other appurtenances.
          Lessor shall, also, be responsible for maintenance of all windows, of
          the roof and its elements, cosmetic appearance and maintenance of the
          exterior, maintenance of all parking areas and the paved surface of
          said parking areas, all landscaping, and components of the building.
          As set forth above, Lessor shall turn over and assign to Lessee all
          warranties and guarantees from all suppliers, contractors, and workmen
          with respect to any improvements to the building and premises paid for
          by the Lessor.

          Lessor shall be responsible for the structural elements of the
          exterior of the building; as well as for apparatus, piping or wiring
          delivering utilities from the public way to the edge of the building

     f.   Reference is herein made to Section 2.6 and Section 3.1 and Section
          3.2 and Section 3.3 and Section 5.2 and Section 5.10 of this
          Indenture.

1.7.2.  Taxes

        LESSEE shall be responsible for all real estate and other taxes assessed
        by any government authority against the real estate (including building,
        land and improvements) leased herein to the Lessee.

        Reference is herein made to the provisions of Section 2.7 of this
        Indenture.

1.7.3.  Insurance and Indemnification

        a.   Lessee, at its sole cost, will maintain, with sufficient limits of
             coverage, fire and casualty loss insurance, insurance against
             liability for losses, damages or injury of any kind to anyone upon
             the premises (or as a result of any activities of the Lessee), and
             coverage against all other insurable risks; except for those
             injuries, losses and damages caused by the fault,

                                       7
<PAGE>
 
          omission, negligence or willful act of the LESSOR or other tenants of
          the LESSOR (i.e. other than the LESSEE herein), as stipulated in
          Section 5.7 (A).

          Lessee shall name the Lessor as an additional insured upon all said
          policies issued by recognized companies licensed to do business in
          Massachusetts; and Lessee shall forward to the Lessor, as each
          contract or policy of insurance shall be issued or renewed, a
          certificate of the said insurance coverage with the Lessor named as a
          payee or insured party in the event of loss or damage.

     b.   Lessee shall indemnify and hold harmless the Lessor against any loss,
          claims or damages resulting from any of the activities of the LESSEE;
          and shall promptly defend against claims resulting therefrom. LESSEE
          shall, and does, indemnify and hold harmless the LESSOR from any said
          losses or damages except for those injuries, losses or damages caused
          by the fault, omission, negligence or willful act of the LESSOR or of
          the tenants of the LESSOR (other than the LESSEE herein); and as
          stipulated in Section 5.7 (A) hereof.

          Lessee shall insure the Lessor from loss of rental income resulting
          from fire or other casualty, as set forth under Section 5.7. (B).

     c.   Lessee shall comply will all relevant laws and legal requirements and
          environmental regulations in the conduct of its operations. Lessee
          shall not expose Lessor to damages, loss or expense as a result of any
          activities of the Lessee - including, but not limited to, use of the
          premises, any of its operations, or any discharges.



     d.   Reference is herein made to the provisions of Section 5.7 of this
          Indenture.

     e.   With respect to the renovations and construction stipulated in the
          "AGREEMENT to IMPROVE and LEASE PREMISES" dated May 19, 1977 (and
          referred to in Section 1.1. hereof);

          (i)   In the event that the contractor or any subcontractor engaged by
                the LESSEE shall default in its obligations or responsibilities,
                and if the insurance coverage furnished by said contractor or
                subcontractor shall not be adequate to cover the losses and
                damages sustained by LESSOR as a result of said default, then,
                in such event, the LESSEE does, and shall, indemnify and hold
                harmless the LESSOR from damages, losses or expenses caused by
                the failure of said contractor or subcontractor with respect to

                                       8
<PAGE>
 
                the work, labor or materials required by said contractor or
                subcontractor.

          (ii)  In the event that any employee or any of the personnel of said
                contractor of subcontractor shall be damaged or injured while in
                the course, or arising out, of the employment of said employee
                or personnel, the LESSEE shall, and does, indemnify and hold
                harmless the LESSOR from any claim, suit or demand made by said
                employee or personnel alleging any failure, negligence, omission
                or action of the LESSEE and of the LESSOR, or both of them, as
                causing or contributing to said injury of damage.

                The LESSEE shall maintain insurance, in responsible companies,
                covering any such claim, suit or demand brought against either
                the LESSEE or the LESSOR, or both of them, for recovery from
                either the LESSEE or the LESSOR (or both) as third parties on
                account of said injury of damage resulting from said industrial
                accident.

1.8. LESSEE'S Utilities:

     Lessee shall be solely and exclusively responsible for any and all
     utilities furnished or provided to the leases premises. Without limitation,
     said utilities shall include electricity, water, heating fuel, and any
     other service provided to the leased premises. Lessee shall be solely
     responsible for the maintenance and repair of all equipment, lines or
     apparatus employed to provide and distribute said utilities and service
     within the leased premises. (Excluded from the provisions aforesaid is the
     Waste Water Treatment Facility which Facility shall be governed by the
     provisions of Section 1.14 hereof).

     The obligations of the LESSEE to pay for any and all utilities furnished or
     provided to the premises leased hereunder shall begin as of the date the
     renovations and construction referred to in the Agreement of May 19, 1997
     (Section 1.1) shall have been commenced. The LESSEE shall, therefore, be
     responsible, and shall pay for, all said utilities (including, but not
     limited to, electricity) furnished to the premises leased hereunder from
     the date of commencement of the renovations and construction referred to in
     said Agreement dated May I 9, 1997 until and through the termination date
     (including termination dates of extended terms) of this Indenture of Lease.

     Reference is herein made to the provisions of Section 2.8 of this
     Indenture.

1..9. POSSIBLE EXPANSION:

     Reference is here made to the Agreement of May 19, 1997, Section I
     ("POSSIBLE EXPANSION")

                                       9
<PAGE>
 
     Provided that said expansion shall be feasible, when requested by the
     Lessee, the Lessor will construct an expansion or extension (of not more
     than 40,000 square feet of floor space) to the east of the building if
     required by the Lessee; subject, however, to the following conditions: -



     1.   The Lessor shall be able to secure financing for said expansion from a
          conventional banking institution at then current rate of interest;
     2.   The expansion shall be permitted under all applicable laws and
          regulations-including zoning and building requirements;
     3.   All required permits shall be issued -- including approvals from
          environmental regulatory agencies, state, federal (if necessary) and
          municipal authorities, and any other governmental body that may have
          oversight responsibilities.
     4.   The Lessor and the Lessee shall agree upon the rent, terms and
          conditions of the Lease affecting the present premises herein leased
          and, also, said possible expansion.
     5.   The cost of moving pipes, tubes, wires, valves and any and all devices
          that now service the Waste Water Service Facility, the Fire Protection
          Station and any other support systems for the buildings upon the site
          shall be an expense attributable to the construction costs of the said
          expansion; and shall be factored into the agreed upon rent.

          The obligation to construct said expansion is upon the condition that
          said devices can be moved; that the relevant easements and rights of
          way or access may be relocated along a new path; and that the
          easements and rights of way or access to service same shall be
          established and confirmed in their new path or location with the
          written consent of all parties that may have an interest therein.

          Said relevant easements and rights of way or access shall include, but
          shall not be limited to, the easements and rights of way and access to
          be granted by the Lessor to LOCKHEED MARTIN CORPORATION ("LOCKHEED")
          in order to facilitate the remediation activities to which LOCKHEED is
          committed, and as set forth in Section 1.12 and in Section 1.13.

     6.   It is anticipated that within the area upon which said expansion may
          be requested LOCKHEED shall be engaged in remediation of shallow
          groundwater contamination associated with underground storage tank
          maintained by CONVERSE, INC. LOCKHEED is expected to agree, if the
          Lessor seeks to develop said area, to modify and move its groundwater
          remediation equipment, at its expense, so long as said modification
          and movement is

                                       10
<PAGE>
 
         (i)    essential to said development;

         (ii)   is consistent with LOCKHEED'S remediation obligations;

         (iii)  does not pose an unreasonable risk to human health or to the
                environment;

         (iv)   does not unreasonable prolong remediation activities.

   6.    The Lessee shall have the right to secure or provide the financing for
         said expansion if the Lessor shall be unable to secure same. In the
         event that the said expansion shall be financed by the Lessee, the base
         rent established for said expansion shall be adjusted to reflect any
         cost incurred by the Lessee with respect to said financing and shall be
         appropriately adjusted to said circumstances.

         (Said possible extension is outlined on EXHIBIT B hereto attached.)

1.10.  OPTION TO EXTEND LEASE: (subject and pursuant to the provisions of
       Section 8.20)

       Subject to the conditions set forth in Section 8.20 (A), and provided
       that the Lessee shall not then in default of any of the terms of this
       lease (and provided, further that the Lessee shall give written notice of
       its decision to extend the lease), the Lessee has, and shall have, two
       (2) successive options to extend the lease each for a term of five (5)
       years upon the same terms and conditions of the original ten (10) year;
       term in accordance with the provisions set forth in section 8.20 of this
       Indenture of Lease. However, the rent for each of the said two (2)
       extended five (5) year terms shall be established, as hereinafter
       stipulated and as stipulated in Section 8.20 of this Indenture.

       The partied do herewith stipulate and agree:

       A.   With respect to the rent during the two (2) extended five (5) year
            terms: -

            1.  During the first of said two five (5) year option terms,
                (commencing December 1, 2007 and ending November 30,2012) the
                base rent during said five (5) years shall be established at the
                rate of ninety five (95%) percentum of the then market rent for
                said leased premises. (See Section 8.20 (B).)

            2.  During the second of said two (2) year option terms, (commencing
                December 1, 2012 and ending November 30, 2017) the base rent
                during said second five (5) year term shall be the then market
                rent. (See Section 8.20 (C).)

       B. Notice


            It is agreed that the extension of the lease for said two (2)
            extended terms is, and shall be, upon the condition that the Lessee
            shall deliver to the Lessor written notice of its intention and
            decision to extend the term of this lease no later than one (1) year
            prior to the termination

                                       11
<PAGE>
 
            date of the then term of the lease, as stipulated in Section 8.20
            (B) and Section 8.20 (C) hereof.

            Accordingly, with respect to the first extended term of five (5)
            years, the Lessee shall give written notice to the Lessor of its
            decision to extend the lease for said five (5) year term no later
            than November 30, 2006. With respect to the second extended term of
            five (5) years, the Lessee shall give written notice to the Lessor
            of its decision to extend the lease for said second five year term
            no later than November 30, 2011. (See section 8.20)



1.11  SUBLEASING (subject to the provisions of Section 5.6 through Section
      5.6.6)

       The Lessee shall not assign or sublease or sublet the premises or any
       portion thereof unless, in each instance, the Lessor shall have given its
       approval in writing to said sublease or subletting: which approval shall
       not be unreasonably withheld, and as provided in Section 5.6 of this
       Indenture of Lease.

       In the event that the rent for said portion subleased or sublet shall
       exceed the rent paid to the Landlord, the increment shall be retained by
       the LESSEE.

       The provisions of this Indenture of Lease, set forth in Section 5.6
       through Section 5.6.6. shall govern and determine assignment, subleasing
       or subletting of this lease. No such assignment, subleasing or subletting
       shall be permitted unless same shall comply with the said provisions
       (Section 5.6 through Section 5.6.6.)



1.12  ENVIRONMENTAL - 21E, etc.

      Reference is made to Section L ("ENVIRONMENTAL - 21E -Etc.") of the
      Agreement of May 19, 1997

      1.  The parties are aware that the site upon which the facilities are
          located has been under review by the Department of Environmental
          Protection ("DEP"); and that the former occupant, GENERAL ELECTRIC
          COMPANY ("G.E."), was named the Responsible Party in a Notice of
          Responsibility dated June 11, 1986. Subsequently, the Lessor received
          a Notice of Responsibility ("N.O.R.") from DEP dated April 16, 1991
          occasioned by bankruptcy proceeding instituted by the parent company
          of Converse, Inc. (Sublessee with respect to G.E. of Building No.2.)

      2.  The contamination of the site resulted from releases of gasoline, oil
          and other substances by G.E. and its sub-lessee, Converse, Inc.

      3.  G.E. accepted and assumed the responsibility to conduct remediation
          activities in 

                                       12
<PAGE>
 
          accordance with plans submitted to, and approved by, D. E. P.
          (including matters referred to in the N. O. R. mailed to the Lessor
          dated, as stated, April 16, 1991 and occasioned by the bankruptcy
          proceedings aforesaid). This responsibility has been expressly
          acknowledged and assumed by the successors to G.E., i.e., MARTIN
          MARIETTA CORPORATION and its successor, LOCKHEED MARTIN CORPORATION
          ("LOCKHEED").

          LOCKHEED is committed to (and is engaged in) the necessary remediation
          process as approved by, and under the oversight of, D. E. P.

      4.  Lessor will seek reports of the engineers engaged by LOCKHEED. These,
          as well as progress reports relating to the remediation activities as
          received by the Lessor, shall be submitted by the Lessor to the
          Lessee.

      5.  LESSOR shall indemnify the Lessee from any claims made by third
          parties unrelated and not in privity to Lessee arising out of any
          contamination of the site that has occurred prior to the occupancy of
          the leased premises by the Lessee. The Lessor and the Lessee shall
          consult and co-operate with each other in the event that any such
          claims shall arise.

      6.  The parties acknowledge that the Lessor is currently engaged in
          negotiations with LOCKHEED with respect to the continuing
          responsibility of LOCKHEED (subject to the oversight of the D. E. P.)
          and to confirm and define liability, indemnification and the nature of
          related documentation and agreements that may be agreed upon. Lessee
          agrees to cooperate with respect thereto if requested in order that
          remediation activities shall continue and be facilitated to further
          the best interests of the parties.

      7.  In connection with the response and remediation activities upon the
          Facilities to which LOCKHEED is committed, the Lessor reserves the
          right to agree to permanent Activity and Use Limitations ("AUL"), as
          shall be specified and agreed upon, with respect to certain specific
          areas within the said Facilities or Complex. Said AUL shall be
          consistent with the Massachusetts Contingency Plan, 30 C.M.R. Section
          40,00, et seq ("MCP") and approved by the DEP. The Lessee
          acknowledges herewith that the Lessor has reserved, and does reserve,
          the right to agree to said AUL in connection with the continuing
          responsibility of LOCKHEED and the remediation response and activities
          in which LOCKHEED is, and shall be, engaged.

      8.  The Lessee shall comply strictly with all relevant Environmental
          Control Laws.

          In particular, and without limitation, the Lessee shall comply with,
          and shall be subject to,

          a. the Comprehensive Environmental Response, Compensation, and
             Liability Act of 1980 (CERCLA"), as amended by the Superfund
             Amendment and Reauthorization Act of 1986, 42 U.S.C. Section 9601
             et seq.; and

                                       13
<PAGE>
 
          b. the Massachusetts Oil and Hazardous Materials Release Prevention
             and Response Act, as amended, Massachusetts General Laws,
             Annotated, Chapter 21 E.

          In connection with the foregoing, the Lessee shall comply with the
          provisions set forth in Section 5.3.

1.13  EASEMENTS AND RIGHTS OF ACCESS

    A. Lessor shall retain existing easements and rights of way over the
       facilities and the premises (and shall reserve additional easements and
       rights of access) in furtherance of its management obligations and
       oversight - including right to pass and re-pass over and to be and to
       remain upon the premises to perform work upon, and to service, water and
       fire protection facilities and lines, Waste Water Treatment Facility, and
       for any other purpose required by the Lessor. Easements and rights of
       access have been granted for this purpose to AMETEK, as successor to G.
       E. Further, Lessor retains, and shall have, the right to grant easements
       in connection with said management and oversight (including easements to
       LOCKHEED MARTIN CORPORATION in order to facilitate its remediation of the
       site as required by D. E. P. - See 1.12 above).

       Said easements and rights of access shall not unreasonably interfere with
       the business activities of the Lessee.

    B. To facilitate the remediation activities to which LOCKHEED is committed
       (and in which it is now engaged), as indicated in Section 1.12, the
       Lessor intends to grant, and shall grant, right of access over and upon
       the Facilities or Complex of which the premises leased hereunder are a
       part. The easement to be granted to LOCKHEED shall include the right to
       pass and repass, the right to remove soil and the right to engage in soil
       vapor extraction activities as well as creek sediment remediation.

       The Lessee does herewith agree and consent to the grant of said easement,
       right of access and right to pass and repass to LOCKHEED to facilitate
       said remediation; and the Lessee shall not interfere with, or impede, the
       grant of said easement or the remediation conducted in connection
       therewith.

    C. The LESSEE shall permit the other LESSEE in the Complex (that is, AMETEK)
       to pass and repass over the premises leased to GENERAL SCANNING, INC. to
       enable AMETEK to have access to the Waste Water Treatment Facility and to
       the other northerly portions of the Complex that are leased to AMETEK, as
       shown on EXHIBIT A; provided that this right of access granted to AMETEK
       shall not be used in such manner as to unreasonable interfere with the
       business activities of the LESSEE (i.e. GENERAL SCANNING, INC.).

1.14. WASTE WATER TREATMENT FACILITY

    Reference is made to Section N ("WASTE WATER TREATMENT FACILITY") of the
    Agreement, dated May 19, 1997.

                                       14
<PAGE>
 
       1. Said Building No.2 is serviced by a new and "state of the art" Waste
          Water Service Facility (placed on line within the last year) and
          located northeast of said Building No.2 (The expected life of said
          facility - - about thirty years-).

       2. Lessor shall assume cost of providing service of said facility to
          Lessee, including costs of its operation and ordinary maintenance.
          Said costs shall be shared with the other tenant of the Facilities,
          AMETEK AEROSPACE PRODUCTS, INC. ("AMETEK"); provided only, however,
          that in the event a replacement of the said facility (beyond
          maintenance and operation) the tenants using same shall be responsible
          for said replacement and shall contribute thereto upon the agreed upon
          the formula established to determine use and allocation of costs of
          operation (to be based upon degree of usage and employee population of
          the Tenants).

          During the first ten (10) years of the term of the lease, however,
          Lessee shall have no responsibility with respect to replacement of the
          facility.

       3. In the event that there shall be any damage, dysfunction or loss to
          the said Waster Water Treatment Facility caused by any use, activities
          or misuse by the Lessee or any of its personnel, representatives or
          employees, the Lessee shall indemnify the Lessor with respect to said
          damage, dysfunction or loss; and shall make the necessary payments to
          rectify said damage, dysfunction or loss

       4. Lessee will pay that share of the real estate or other taxes assessed
          against said Waste Water Treatment Facility (in the event that any
          shall be assessed or levied in respect thereto) equivalent to the
          percentage of operational and management costs thereof attributable to
          the Lessee.

       5. The LESSEE shall be designated, and shall be included, as a permitted
          user of said Waste Water Treatment Facility. In connection therewith,
          the LESSEE shall execute and deliver any and all documents, including,
          but not limited to, applications, permit or license agreements, and
          shall do all things that shall be required, in order that the LESSEE
          shall be properly designated as a permitted user of said Facility.

          The LESSEE shall assume, and shall comply with, all obligations
          imposed upon the LESSEE under applicable Law as a permitee or
          permitted user of said Waste Water Treatment Facility.

       6. The LESSEE shall keep and maintain in full standing business
          interruptions insurance that shall cover or reinstate the Lessee from
          any damages or losses resulting from interruptions of its business
          activities.

          In the event that any interruption of the business activities of the
          LESSEE shall result from, or be attributable to, any failure or
          disruption of, or damage to, said Waste Water Treatment Facility, the
          LESSEE shall make no claim against the LESSOR and shall not look to
          the LESSOR for recovery of any damages or loss resulting therefrom.
          The LESSEE agrees that it shall look for recovery for said damages or
          loss to its insurance covering losses from business

                                       15
<PAGE>
 
          interruption (including interruptions caused by said disruption or
          failure of said Waste Water Treatment Facility).

          The LESSEE agrees that it shall not seek indemnification against said
          losses or damages from the LESSOR.



1.15  PERMITTED USES:

      The Lessee use the leased premises for the following permitted uses:
        a. General office purposes and,
        b. Subject to the provisions of Section 5.3(B) hereof; light
           manufacturing and research and development purposes.

      The use and occupation of the said leased premises by the LESSEE shall be
      subject to, and in accordance with, the provisions of Section 5.3 (A) (B)
      and (C).

      The Lessee shall maintain and keep the premises leased hereunder in good
      repair and condition; and the Lessee shall not commit or suffer any waste,
      or destruction, or loss to said premises, as stipulated in Section 5.2.
      The Lessee, further, shall NOT permit or suffer any activity that may
      produce hazardous materials and shall not suffer, cause or permit any
      releases or discharges of any hazardous materials or hazardous substances
      upon the Premises, or upon the Facilities as stipulated in Section 5.3.

1.16. INITIAL MINIMUM LIMITS OF LESSEE'S GENERAL LIABILITY INSURANCE: -
      

       Twelve Million ($12,000,000.00) Dollars under a general corporate general
       liability policy.

1.17. RECOGNIZED BROKERS

       Hunneman Commercial Company            Meredith & Grew, Incorporated
       70-80 Lincoln Street                   70-80 Lincoln Street
       Boston, Massachusetts 02111; and       Boston, Massachusetts 02110-1701

1.18  EXHIBITS. There are incorporated as part of this Lease:

      EXHIBIT A  -   Plan Delineating the Premises Leased Hereunder
      EXHIBIT B  -   Plan Indicating Possible Addition to Building No.2.
      EXHIBIT C  -   Agreement dated May 19, 1997 (Section 1.1)
 

                                  ARTICLE II
                                  ------- --

                       BUILDING, PREMISES, TERM AND RENT
                       --------- --------- ---- --- ----
                                        


2.1   The Premises

                                       16
<PAGE>
 
     The Lessor hereby demises and leases to the Lessee, and the Lessee hereby
     leases, rents and accepts from the Lessor, the Premises (i.e. the site).

     Said premises are more particularly described under ARTICLE I hereof; and
     are shown on the plan entitled hereto annexed and incorporated as EXHIBIT
     A. Said leased premises include the one story brick building known as
     Building No.2, along with the parking area and all land appurtenant
     thereto, as shown on said plan.

     Reference is herein made to Section 1.5 of this Indenture of Lease.

2.2  Right To Use Common Facilities

     The Lessee shall have, as appurtenant to the premises herein leased, the
     non-exclusive right to use in common with others, subject to reasonable
     rules of general applicability to tenants of the Facilities from time to
     time made by the Lessor (of which the Lessee is given notice) the
     following:-

     (a)  any common area, common means of egress and access, common loading
          platform, if any, of the Facilities and Complex;
     (b)  the pipes, ducts, conduits, wires and appurtenant meters and equipment
          serving the Premises that relate to or serve the Facilities and
          Complex or that are used in common with others; and 
     (c)  common walkways and driveways necessary for access to, and egress
          from, the premises leased hereunder - including, without limitation,
          access roadway from Concord Street (North Reading), access to and
          egress from the leased premises over parking area to the west of the
          buildings forming Facilities or Complex, and other areas of land
          access to and over which shall be necessary or appropriate for the
          occupancy of the leased premises by the Lessee; and PROVIDED, however,
          that the Lessor shall have reserved said rights or access or egress,
          easements, or rights of way; and, PROVIDED, that the Lessor shall
          have, otherwise, the ability and legal right to grant same to the
          Lessee; and

          The Lessee agrees to co-operate with AMETEK AEROSPACE PRODUCTS, INC.
          and with the Lessor to establish restrictions, conditions and terms of
          use, right to pass and repass, and control over the access roadway
          from Concord Street (North Reading) into the Facilities or Complex to
          promote the security, convenience and the best interests of all
          parties.

     (d)  Access to, connection with and right to services of the Waste Water
          Treatment Facility referred to in Section 1.14 of this Indenture;
          PROVIDED, however, that the LESSEE shall be a permitted user thereof
          and shall be designated and established as such permitted user.

          In connection therewith, the LESSEE shall execute all documents,
          including applications and licenses, in order to establish itself as a
          permittee or permitted user of said Waste Water Treatment Facility. As
          such lawful or permitted user or permittee, the LESSEE

                                       17
<PAGE>
 
          shall comply with all relevant obligations and duties in respect
          thereto imposed by any applicable law or ruling.

          (See, also, Section 1.1 3C for right to pass and repass reserved for
          AMETEK.)

     (c)  Provided that the Town of Wilmington shall grant right of access and
          right to install and construct a driveway or passageway from Fordham
          Road, Wilmington on to the premises leased hereunder, the Lessee shall
          have the right to use and pass and repass over said driveway or
          passageway; provided that the Lessee shall maintain said driveway or
          passageway and keep it in good repair.

2.2.1  Lessee's Parking

     In addition, the Lessee shall have the right to use the Parking Areas arid
                                                                     -----     
     Parking Spaces shown on the plan annexed hereto as EXHIBIT A. With respect
     to any parking facilities or spaces pertaining to the entire Facilities or
     Complex, said areas or spaces shall not be used or occupied by the Lessee
     or any of its personnel or representatives without the specific prior
     approval, in writing, of the Lessor and of the other Lessees of the Lessor
     in said Facilities or Complex.

     The Lessee covenants and agrees that It and all persons claiming by;
     through and under it, shall at all times abide by all reasonable rules and
     regulations promulgated by Landlord with respect to the use of the parking
     areas on the Site. The parking privileges granted herein are non-
     transferable.

     Further, the Lessor shall have no responsibility whatsoever for loss or
     damage due to fire, theft or otherwise to any automobile(s) parked on the
     Site or to any personal property therein, however caused, and the Lessee
     covenants and agrees, upon request from Lessor from time to time, to notify
     its officers, employees, agents and invitees of such limitation of
     liability.

     The Lessee shall be solely and exclusively responsible for security and for
     the safety of any and all motor vehicles and the contents thereof that
     SHALL use any of the parking spaces within the leased premises or that may
     be used by the Lessee in other parking areas or the Facilities or Complex
     with approval by the Lessor and other Lessees in said Facilities or
     Complex.

2.3  Lessor's Reservations (Repairs, etc.)

     The Lessor reserves the right from time to time, without unreasonable
     interference with Lessee's use and without causing a continuous, prolonged
     and material interruption with Lessee's use:

     (a)  to install, use, MAINTAIN, repair, replace and relocate for service to
          either or both the Premises and other parts of the Facilities, pipes,
          duets, conduits, wires and appurtenant fixtures wherever located in
          the Premises (the "Site") or the Facilities Of the Complex; and

     (b)  to alter or relocate any other facilities used in common with other.

                                       18
<PAGE>
 
2.4  Habendum

     The Lessee shall have and hold the premises leased hereunder for a period
     of ten (10) years commencing on the Commencement Date, and continuing for
     the said ten (10) year term unless sooner terminated as provided in Article
     VI or Article VII or unless extended as provided in Article I (Section 1.10
     and ARTICLE VII (Section 8.20)).

2.5  Monthly Fixed Rent Payments

     The Lessee agrees to pay, and shall pay, to the Lessor, in the amounts set
     forth under Section 1.6 and Section 1.6.1. and Section 1.6.2. of this
     Indenture, or as directed by Lessor, at Lessor's Original Address specified
     in Section 1.1 hereof, or at such other place as Lessor shall, from time to
     time, designate by notice to the Lessee:

     (1)  on the Commencement Date (defined in Section 1.1 hereof) and
          thereafter monthly, in advance, on the first day of each and every
          calendar month during the Original Term, a sum equal to one twelfth
          (1/12th) of the Annual Fixed Rent (sometimes hereinafter referred to
          as "fixed rent") in the amounts established under ARTICLE I, of this
          Indenture of Lease.

     (2)  on the first day of each and every calendar month during the extension
          option period (if exercised), a sum equal to one twelfth (1/12th) of
          the annual fixed rent as determined in Section 1.10 and in Section
          8.20 for the each of the two five (5) year extension option periods.

     Until notice of some other designation is given, fixed rent and all other
     charges for which provision is herein made shall be paid by remittance
     payable to, or for the order of;

                          THE WILMINGTON REALTY TRUST



                          C/O MRS. LUCY PHYLLIS BOMBA
                          20 LAWNDALE ROAD
                          STONEHAM, MASSACHUSETTS 02180

     Annual Fixed Rent for any partial month shall be paid by Lessee to Lessor
     at such rate on a pro rata basis, and, if the Commencement Date is a day
     other than the first day of a calendar month, the first payment which the
     Lessee shall make to Lessor shall be a payment equal to a proportionate
     part of such monthly Annual Fixed Rent for the partial month from the
     Commencement Date to the first day of the succeeding calendar month.

     Other charges, if any, payable by Lessee on a monthly basis, as hereinafter
     provided, likewise shall be prorated, and the first payment on account
     thereof shall be determined in similar fashion but shall commence on the
     Commencement Date; and other provisions of this Lease calling for monthly
     payments shall be read as incorporating this undertaking by Lessee.

     The Annual Fixed Rent and all other charges for which provision is herein
     made shall be paid by

                                       19
<PAGE>
 
     The Annual Fixed Rent and all other charges for which provision is herein
     made shall be paid by Lessee to Lessor, without offset, deduction or
     abatement except as otherwise specifically set forth in this Lease.

2.6  Lessee Responsible For Maintenance, etc.

     The Lessee is, and shall be, solely and exclusively responsible, and shall
     promptly pay, all charges and expenses necessary or incurred for the
     cleaning and maintaining of any and all of the leased premises, including
     the interior and exterior of the building, parking areas, and other
     appurtenances. The Lessee, at its sole and exclusive cost, shall promptly
     remove snow and ice from the said premises, and shall maintain and keep in
     first class condition all landscaping, the exterior of the building,
     including all glass, all parking areas, roadways and access roads and
     driveways. In furtherance of the covenants set forth under ARTICLE
     1(1.7.1.), the Lessee shall be responsible for the maintenance and upkeep
     of the leased premises as therein stipulated.

2.7  Real Estate Taxes; Payment:

     During the initial ten (10 year term of the lease and during any all
     extended terms thereof; the Lessee shall pay all and any real estate taxes
     and any other taxes (if any there be) that shall be assessed or charges by
     any governmental agency or authority in respect to, or against, all or any
     portion of, premises hereunder leased to the Lessee.

     Said taxes shall be paid by the Lessee directly to the municipality or
     other taxing authority that shall make or levy said charge. The said
     payments shall be made promptly and as due; and if the tax charge shall be
     made in installments, said installments shall be paid promptly and as due.
     Any interest or penalty occasioned by late or delinquent payment shall be
     paid by the Lessee.

     Lessee shall promptly forward to the Lessor evidence of payment of each tax
     bill or levy by delivering to the Lessor a copy of the receipted tax bill
     or tax levy.

     The parties shall request of the taxing authorities that the entire
     premises leased to the Lessee (as shown on said plan) be established as a
     separate parcel (or separate parcels) for tax purposes; and that the entire
     premises herein leased to the Lessee be taxed as a separate and distinct
     entity (or as separate and distinct entities). In the event that any
     portion of premises leased to the Lessee hereunder shall not be separately
     assessed, or in the event that any portion of said leased premises shall
     not be assessed as part of the premised hereunder leased to the Lessee,
     then, in such event, the tax attributable to said portion leased to the
     Lessee shall be established and the tax attributable to said portion shall
     be paid by the Lessee.

     Terms used herein are defined as follows:

          (a)  "Tax Year" means the twelve-month period beginning July 1 each
               year during the Term or if the appropriate governmental tax
               fiscal period shall begin on any date other than July 1, such
               other date.

                                       20
<PAGE>
 
          (b)  "Real estate taxes" means all taxes and special assessments of
               every kind and nature assessed by any governmental authority on
               the Premises which the Lessor shall become obligated to pay
               because of or in connection with the ownership, leasing and
               operation of the Premises and reasonable expenses of any
               proceedings for abatement of taxes. The amount of special taxes
               or special assessments to be included shall be limited to the
               amount of the installment (plus any interest, other than penalty
               interest, payable thereon) of such special tax or special
               assessment required to be paid during the year in respect of
               which such taxes are being determined. There shall be excluded
               from such taxes all income, estate, succession, inheritance and
               transfer taxes.

2.7.1  Tax Abatement - Procedure

       The Lessee shall pay, as aforesaid, all real estate or other taxes upon
       the premises leased hereunder.

       In the event that the Lessee shall be aggrieved by any tax levied or
       assessed against or upon the premises leased hereunder (or any portion
       thereof), and if the Lessee shall seek to protest said tax or said
       assessment or shall seek to abate or secure relief from said tax or
       assessment, the Lessee shall follow the procedure described herein, to
       wit:

       1.   The Lessee shall promptly notify in writing the Lessor of its desire
            or intention to protest said tax or assessment and to abate or seek
            relief with respect thereto; setting forth in said notice the
            specific taxes, assessment or valuation protested and the basis or
            reasons for said protest.

       2.   The Lessee may, thereafter in its name only, appeal any action or
                                       ----------------                      
            inaction of said taxing authority upon its said application for
            abatement to the Appellate Tax Board and by appeal or Petition to
            the Court of competent jurisdiction for a review of said tax, or
            said assessment, or said action or inaction by said taxing
            authority; and for relief therefrom.

       3.   The Lessee shall, notwithstanding, continue to pay all taxes when
            and as due, as hereinbefore stipulated; and shall continue to make
            payment of all taxes as levied or assessed by the taxing authority.

       4.   All costs or expenses incurred in the process of instituting any
            said tax abatement proceedings or appeals or any action taken to
            protest or review taxes, or valuations or assessments made with
            respect to the premises leased hereunder shall be borne solely and
            exclusively by the Lessee. The Lessee shall pay all expenses
            resulting from said action or proceedings, including, but not
            limited to, counsel fees, engineers' fees, appraisers' fees and any
            other costs incidental to such litigation and proceedings.

       5.   All recovery and all proceeds resulting from any proceedings brought
            or instituted for abatement of said taxes shall belong, and shall be
            paid, to the Lessee.

                                       21
<PAGE>
 
2.8  Lessee's Electricity and Utilities

     The Lessee covenants and agrees to take all steps required by the
     appropriate utility company to provide for the direct billing to the Lessee
     of the electricity serving the premises leased to the Lessee. The Lessee
     covenants and agrees to pay, punctually as and when due, all charges for
     electricity and other utilities furnished to the leased premises. The
     Lessee covenants and agrees to defend, save harmless and indemnify the
     Lessor against all liability, cost and damage arising out of or in any way
     connected to the payment, non-payment or late payment of any and all
     charges and rates for any and all said utilities.

     The LESSEE shall be responsible, and shall pay, for all utilities supplied
     or furnished to the premises leased hereunder to the Lessee commencing
     with, and as of; the commencement of renovations and construction (as set
     forth in the Agreement dated May 1, 1997, referred to in Section 1.1).


                                  ARTICLE III
                                  -----------    
                                        
                             CONDITION OF PREMISES
                             ---------------------
                                        

3.1  Delivery of Premises

     The Lessor shall deliver the premises leased hereunder to the Lessee in
     prime condition, as stipulated in the Agreement dated May 19, 1997 (Section
     F and Section H); and the Lessee shall have no responsibility, thereafter,
     to perform any additions, alterations or improvements in the Premises or
     for the repair or maintenance of said premises, as stipulated in said
     Agreement (except as stated herein under ARTICLE I - Section 1.9. with
     respect to possible expansion).

3.2  Alterations and Additions

     This Section 3.2 shall apply to the preparation of the premises for use by
     the Lessee as stipulated in the Agreement dated May 19, 1997 and for the
     Term of the lease (including initial and extended terms), except for minor
     repairs and ordinary maintenance and upkeep.

     The Lessee shall not make alterations and additions to leased premises
     except in accordance with plans and specifications therefor first approved
     by Landlord, which approval shall not be unreasonably withheld.

     The Lessee, before commencement of work, shall secure all licenses and
     permits necessary therefor; deliver to the Lessor a statement of the names
     of all its contractors and subcontractors and the estimated cost of all
     labor and material to be furnished by them and security satisfactory to the
     Lessor protecting the Lessor against liens arising out of the furnishing of
     such labor and material. The Lessee shall require and cause each contractor
     to carry workmen's compensation

                                       22
<PAGE>
 
        Lessee shall carry and maintain commercial general liability insurance,
        or comprehensive general liability insurance with a broad form
        comprehensive liability endorsement with such limits as the Lessor may
        reasonably require, but in no event less than $1,000,000.00 combined
        single limit per occurrence on a per location basis (all such insurance
        to be written in companies approved by the Lessor and naming and
        insuring Lessor as an additional insured and insuring the Lessee as well
        as the contractors). The Lessee shall deliver to the Lessor certificates
        of all such insurance.

        The Lessee agrees to pay promptly when due the entire cost of any work
        done on the Premises by Lessee, its agents, employees, or independent
        contractors, and not to cause or permit any liens for labor or materials
        performed or furnished in connection therewith to attach to the Premises
        or the building or the Site or the Facilities and immediately to
        discharge any such liens which may so attach.

        The LESSEE shall pay, as additional rent, 100% of any real estate taxes
        resulting from said alterations or additions.

3.3     General Provisions Applicable to Construction

        All construction work required or permitted by this Lease (or by the
        Agreement between the parties dated May 19, 1997) shall be completed in
        a good and workmanlike manner and in compliance with all Legal
        Requirements and Insurance Requirements now or hereafter in force. Each
        party may inspect the work of the other at reasonable times and shall
        promptly give notice of observed defects. Each party authorizes the
        other to rely in connection with design and construction upon approval
        and other actions on the party's behalf by any Construction
        Representative of the party named in Article I or any person hereafter
        designated in substitution or addition by notice to the party relying.
        The Lessee shall carry and maintain contracts or policies of insurance
        naming both the Lessee and the Lessor as insureds, and covering both the
        Lessee and the Lessor in the event of any claim for injury or damages
        brought by any employee or personnel (as stipulated in Section 1.7.3).


                                  ARTICLE IV
                                  ----------
                                        
                            COVENANTS OF THE LESSOR
                            ----------------------- 
                                        

4.1     LESSOR COVENANTS:

4.1.1.  Delivery of Premises

        The Lessor shall provide and deliver the premises leased hereunder to
        the Lessee for the term herein specified under the covenants herein set
        forth - including rights of way, easements and rights of access and
        egress but only to the extent to which the Lessor may legally confer
        said rights of way, easements and rights of access and egress upon the
        Lessee.

4.1.2.  Quiet Enjoyment

                                       23
<PAGE>
 
       The Lessor shall not interfere with, or impede, the quiet enjoyment of
       the leased premises by the Lessee pursuant the provisions of this
       Indenture of Lease. (Reference is made to the provisions of Section 8.4
       of this Indenture)

4.1.3  Structural Elements of the Exterior

       The Lessor shall be responsible for the structural elements of the
       exterior of the building leased hereunder; as well as for apparatus,
       piping or wiring delivering utilities from the public way to the edge of
       the building,

       Lessee, however, shall be responsible for all said apparatus, piping or
       wiring within any portion of the building.
              ------                             

       The foregoing is subject to the provisions of Section 2.3 of this
       Indenture.



                                   ARTICLE V
                                   ---------

                            COVENANTS OF THE LESSEE
                            -----------------------


       THE LESSEE COVENANTS AND AGREES that during the term and such further
time as Tenant occupies any part of the Premises, the Lessee shall comply with,
shall be obligated to perform, and shall be bound by, each of the
responsibilities herein after set forth under this ARTICLE V. (Section 5.1
through Section 5.13). The Lessee specifically promises, covenants and agrees:

5.1    Payments

       The Lessees shall pay, as and when due, all fixed rent and additional
       rent and all charges for utility services rendered to the Premises in
       accordance with the terms of this Indenture of Lease.

5.2    Maintenance of the Premises Leased Hereunder; Yielding of Premises; Waste
       and Destruction

       The Lessee shall keep the Premises in good order, repair and condition,
       reasonable wear and tear only excepted, and all glass in windows, both
       exterior and interior, and doors of the Premises whole and in good
       condition with glass of the same type and quality as that injured or
       broken, damage by fire or taking under the power of eminent domain only
       excepted. At the expiration or termination of this Lease, the Lessee
       shall peaceably yield up the Premises all construction, work,
       improvements, and all alterations and additions thereto in good order,
       repair and condition, reasonable wear and tear only excepted, first
       removing all goods and effects of the Lessee, and to the extent specified
       by the Lessor by notice to the Lessee given at least ten (10) days before
       such expiration or termination, the wiring for the Lessee's computer,
       telephone and other communication systems and equipment and all
       alterations and additions made by Lessee and all partitions, and
       repairing any damage caused by such removal. The LESSEE shall, upon

                                       24
<PAGE>
 
       termination of the lease term, restore the Premises and leave them broom
       clean.

       The Lessee shall not permit or commit any waste, destruction, loss or
       damage to the premises leased hereunder.

       The Lessee shall be responsible for the cost of repairs which may be made
       necessary by reason of damage to common areas in the Facilities caused by
       the Lessee, its contractors, employees, personnel or invitees.

5.3    Use and Occupation of Leased Premises

   (A) PROHIBITIONS AND RESTRICTIONS

          Continuously and from the commencement of the initial Term and during
          the two (2) extended terms hereof; the Lessee shall use and occupy the
          premises leased hereunder in accordance with the Permitted Uses
          (Section 1.15); subject to Section 5.3(B) below.


       The lessee shall not:-

       (1) injure or deface the Premises, or any other part of the Facilities or
           Complex of which said premises are a part;
       (2) permit in the Premises or on the Site any auction sale, or
           inflammable fluids or chemicals, or nuisance, or the emission from
           the Premises of any objectionable noise or odor;
       (3) use or devote the Premises or any part thereof for any purpose other
           than the Permitted Uses;
       (4) use or devote the leased premises for any use which shall be
           inconsistent with the maintenance of the Building (and the leased
           premises) as an office/research and development building (including
           light manufacturing) of the first class in the quality of its
           maintenance, use and occupancy;
       (5) use or devote any portion of then leased premises for any use or
           purpose which is improper, offensive, contrary to any law or
           ordinance;
       (6) use or devote the leased premises for any purpose or activity that
           may or shall be liable to invalidate or increase the premiums for any
           insurance on the Premises or their contents or liable to render
           necessary any alteration or addition to the Premises.


   (B) ENVIRONMENTAL CONTROL LAWS- the Lessee shall not be in violation of, and
        shall comply with, all laws and rules concerning any and all hazardous
        substances and environmental regulations (including, without limitation,
        CERCLA and M.G.L. Chapter 21E, as set forth in Section 1.12 (8), and,
        as follows:-

       The Lessee shall not engage in (and the Lessee shall not permit, allow or
       suffer, its employees, personnel, representatives, invitees or
       contractors to engage in) any activity that may produce hazardous
       material, waste or substance, or keep or maintain any substance which is
       now, or may hereafter be classified, a hazardous material, waste or
       substance under federal, state or

                                       25
<PAGE>
 
     local laws, rules and regulations, including, without limitation, 42 U.S.C.
     Section 6901 et seq, 42 U.S.C. Section 9601 et seq, 49 U.S.C. Section 1802
     et seq and, also, Massachusetts General Laws, Chapter 21E, (including tile
     rules and regulations promulgated under any of the foregoing Federal, state
     and local laws), as such laws, rules and regulations may be amended from
     time to time (and relating to "Hazardous Substances", as defined in 42
     U.S.C. Section 9601 et seq and to "Hazardous Materials", as defined in
     Massachusetts General Laws, Chapter 21 E). The Lessee shall comply with the
     foregoing; and shall cause its employees, personnel, representatives,
     invitees, agents and contractors to comply with each of said laws, rules
     and regulations.

     Under no circumstances, shall the Lessee cause, suffer, permit or allow any
     discharges or releases upon any portion of the premise leased hereunder of
     any such hazardous materials or hazardous substances. Under no
     circumstances shall the Lessee cause, suffer permit or allow any releases
     or discharges upon any portion of the premises leased hereunder that are
     now, or may in the future be, proscribed or prohibited under any federal,
     state, county or municipal law or regulation.

     Without limitation, the LESSEE shall not cause, suffer or permit any
     releases or discharges of any substances, or cause, suffer or permit any
     actions, that may pollute or cause damage of any kind to the Premises, to
     the Site, or to the Complex or Facilities. The Lessee shall permit or
     suffer no discharges or releases upon the Premises or upon the Facilities
     of any substance prohibited by any applicable law; and shall not engage in,
     or permit or suffer any accumulations, maintenance, releases or discharges
     upon the said Premises or upon said Facilities in violation of any
     applicable law or regulation, federal, stale or local.

(C)  Light manufacturing and research and development uses:

     With respect to light manufacturing and research and development portions
     of the Permitted Uses, the Lessor agrees that Lessee may use the Premises
     for such purposes provided that, upon the condition, and only so long as:

     (1)  such uses are permitted under applicable laws, by-laws, rules and
          regulations from time to time in effect including, but not limited to,
          the Zoning By-Law of the Town of Wilmington, Massachusetts from time
          to time in effect and the requirements of the Americans with
          Disabilities Act and the regulations thereunder all as may, from time
          to time, be in effect (collectively "Governmental Requirements);
     (2)  Lessee shall comply with all Governmental Requirements;
     (3)  such uses shall not create, cause or produce undue noise or odor, any
          nuisance and shall not interfere with the uses and quiet enjoyment of
          other portions of the Facilities or Complex; and
     (4)  such use shall not impose any cost, material risk or liability upon
          the Lessor (including not increasing the cost of Lessor's insurance
          and not resulting in a cancellation of any of Lessor's insurance). The
          Lessee herewith agrees to be responsible for, and to pay, any and all
          such increased costs; - which costs shall be paid promptly by the
          Lessee.

                                       26
<PAGE>
 
5.4  Obstructions; Items Visible From Exterior; Rules and Regulations

     The Lessee shall not obstruct in any manner any portion of the Facilities
     or Complex not hereby leased or any portion thereof or of the buildings or
     of the Site used by Lessee in common with others. The Lessee shall not,
     without prior consent of Lessor, permit the painting or placing of any
     signs, curtains, blinds, shades, awnings, aerials or flagpoles, or the
     like, visible from outside the Premises. The Lessee shall comply with all
     reasonable Rules and Regulations now or hereafter made by Lessor, of which
     the Lessee has been given notice, for the care and use of the Facilities
     and their appurtenances and approaches. The Lessor agrees that its consent
     shall not be unreasonably withheld or delayed.

5.5  Safety appliances; Licenses; Security Systems;

       The Lessee shall keep the Premises equipped with all safety appliances
       (including a new fire alarm system to be provided by Lessor) that may be
       required by any public authority because of any use made by Lessee other
       than normal office/research and development use. In connection therewith,
       the Lessee shall and procure all licenses and permits so required because
       of such use. Further, the Lessee shall do any work required because of
       such use. It is understood and agreed however, that the foregoing
       provisions shall not be construed to broaden in any way the Lessee's
       Permitted Uses.

       The Lessee shall install, and shall keep and maintain, security systems
       of high quality to provide security to any and all parts of the premises
       leased hereunder to the Lessee. Said systems shall be installed and
       maintained at the sole and exclusive cost to the Lessee.

5.6    Assignment; Sublease (Section 5.C through Section 5.6.6.)

       Except as otherwise expressly provided herein, the Lessee covenants and
       agrees that it shall not assign, mortgage, pledge, hypothecate or
       otherwise transfer this Lease and/or Tenant's interest in this Lease or
       sublet (which terms, without limitation, shall include granting of
       concessions, licenses or the like) the whole or any part of the premises
       leased hereunder. Any assignment, mortgage, pledge, hypothecation,
       transfer or subletting not expressly permitted under, or consented to, by
       the Lessee pursuant to Sections 5.6.1 to 5.6.6 hereunder, shall be void,
       ab initio; shall be of no force and effect; and they shall confer no
       rights to, or in favor of, third parties. In addition, the Lessor shall
       be entitled to seek specific performance, or other equitable relief; with
       respect to the provisions hereof.

5.6.1  Subsidiaries; Affiliated Entities; Merger:

       Notwithstanding the foregoing provisions of Section 5.6 above (but
       subject to the provisions of Sections 5.6.4. and 5.6.5 and 5.6.6
       hereafter), the Lessee shall have the right to assign this Lease or to
       sublet the whole or part of the premises leased hereunder, but only and
       exclusively to:

      (1) a parent or subsidiary corporation of the Lessee;

                                       27
<PAGE>
 
       (2) an affiliated entity in common control with Lessee; or

       (3) a corporation into which Lessee may be converted or with which it may
           merge.

5.6.2  Written Notice of Assignment under Section 5.6.1

       Notwithstanding the provisions of Section 5.6 above, in the event the
       Lessee desires to assign this Lease or to sublet the whole (but not part)
       of the Premises (no partial subletting being permitted other than as
       provided in Section 5.6.1), the Lessee shall deliver to the Lessor
       written notice of its intention to assign or sublet the whole or part of
       the premises leased hereunder, pursuant to the provisions of Section
       5.6.1 above, no less than 90 days prior to the execution date of the
       instrument establishing said assignment or subletting. Said written
       notice shall, with particularity, set forth the name, address and
       specific business activities of the proposed sublessee or assignee; and
       said written notice shall disclose in detail the relationship between the
       Lessee and the proposed sublessee or assignee as well as set forth, with
       specificity, any proposed merger or affiliation with the designated
       sublessee or assignee or subtenant..

5.6.3  No Assignment, Sublease or Subletting Without Prior Written Consent of
       Lessor

       Notwithstanding the provisions of Section 5.6 above, but subject to the
                                                            ---
       provisions of this Section 5.6.3 and the provisions of Sections 5.6.4,
       5.6.5 and 5.6.6 below, the Lessee shall have the right to assign this
       Lease or sublet or sublease the whole (but not part) of the Premises in
       accordance with written notice from the Lessee delivered to the Lessor,
       as stipulated under Section 5.6.4 below; provided that, in each instance,
       the Lessee shall obtain the express prior written consent of the Lessor,
       which consent shall not be unreasonably withheld or delayed. The Lessor
       shall not be deemed to be unreasonably withholding its consent to such a
       proposed assignment or subleasing if any of the following conditions
       shall then prevail, to wit:


          (a)  the proposed assignee or sublessee or subtenant is not of a
               character consistent with the operation of a first class office
               building; or

          (b)  the proposed assignee or sublessee or subtenant is not of good
               character and reputation; or

          (c)  the proposed assignee or sublessee or subtenant does not possess
               adequate financial capability to perform the obligations of the
               Lessee as and when due or required; or

          (d)  the assignee or sublessee or subtenant proposes to use the
               Premises (or part thereof) for a purpose other than the purposes
               for which the premises may be used as stated in Section 1.15; or

          (e)  the character of the business to be conducted or the proposed use
               of the Premises by the proposed assignee or sublessee or
               subtenant
               
                (i)   be likely to increase Operating Expenses for the Property
                      beyond that which the LESSOR now incurs for use by the
                      Lessee;

                                       28
<PAGE>
 
                (ii)  be likely to increase the burden on Building systems or
                      equipment over the burden prior to such proposed
                      subletting or assignment; or subleasing or
                (iii) violate or be likely to violate any provisions or
                      restrictions contained herein relating to the use or
                      occupancy of the premises leased hereunder, (including,
                      but not limited to, the provisions of Section 5.3 hereof);
                      or

          (f)  there shall be existing an "Event of Default" (defined in Section
               7.1).

5.6.4   Notice of Proposed Assignment, Subletting or Subleasing

        The Lessee shall deliver to the Lessor written notice of any proposed
        assignment or sublease or subletting; and said notice shall specify the
        provisions of the proposed assignment or subletting, including, the
        following:-

        (a)  the name and address of the proposed assignee or sublessee or
             subtenant; 
        (b)  in the case of a proposed assignment or subletting pursuant to
             Section 5.6.3, such information as to the proposed net worth and
             financial capability and standing of the proposed assignee or
             sublessee or subtenant as may reasonably be required for the Lessor
             to make the determination referred to in Section 5.6.3 above
             (provided, however, that Lessor shall hold such information
             confidential; - the Lessor, however, having, and hereby being
             granted, and retaining, the right to release said information to
             its officers, accountants, attorneys and mortgage lenders on a
             confidential basis);
        (c)  all of the terms and provisions upon which the proposed assignment
             or subleasing or subletting is proposed to be made;
        (d)  in the case of a proposed assignment or subleasing or subletting
             pursuant to Section 5.6.3, all other information necessary to make
             the determination referred to in said Section 5.6.3 above; and
        (e)  in the case of a proposed assignment or subleasing or subletting
             pursuant to Section 5.6.1 above, such information as may be
             reasonably required by Lessor to determine that such proposed
             assignment or subleasing or subletting complies with the
             requirements of said Section 5.6.1 (said information including, but
             not limited to, the matters set forth in said Section 5.6.1.).

     No partial subletting shall be permitted except as provided in Section
     5.6.1.

     If the Lessor shall consent to the proposed assignment or subleasing or
     subletting, as the case may be, then, in such event, the Lessee may
     thereafter assign sublease or sublet (the whole, but not part, of the
     Premises) pursuant to the notice from the Lessee, given as required
     hereunder; provided, however, that if such assignment or sublease shall not
     be executed and delivered to the Lessee within ninety (90) days after the
     date of the consent by the Lessor, the said consent shall be deemed null
     and void; and the provisions of Sections 5.6.2 and 5.6.3 shall then again
     be applicable and shall thereafter be followed as to the proposed
     assignment or subleasing or subletting.


5.6.5  Consent to Assignment Conditional Upon Guarantee of the Lessee (Payment
       of Rent, etc.):

                                       29
<PAGE>
 
       In addition, in the case of any assignment or subleasing or subletting by
       the Lessee, including, but not limited to, any assignment or subleasing
       or subletting as to which Landlord may consent, such assignment,
       subleasing or subletting (and the consent of the Lessor if given thereto)
       shall be upon the express and further condition, covenant and agreement
       (and the Lessee hereby covenants and agrees) that the Lessee shall
       continue to be liable and be responsible for, the Annual Fixed Rent,
       additional rent and other charges to be paid pursuant to this Indenture
       of Lease and shall continue to be liable and responsible for the
       covenants and obligations of the Lessee under this Indenture of Lease.
       Therefore it is agreed, under Section 5.6.6(A) and (B) and (C), as
       follows:

5.6.6. Responsibility in the Event of Assignment or Subleasing

       (A) It is, and shall be, a condition of the validity of any assignment or
           subleasing or subletting, under Section 5.6.1 above, or consented to
           under Section 5.6.3 above, that the assignee or sublessee or
           subtenant shall agree directly with the Lessor, in form reasonably
           satisfactory to the Lessor, to be bound by all the obligations of
           this Indenture of Lease; including, without limitation, the
                                               ------------------
           obligation to pay the rent and other amounts provided for under this
           Lease and including, without limitation, the provisions under ARTICLE
           V, including, specifically, Section 5.3 and Section 5.6 through 5.6.6
           thereof. In any event, such assignment or subleasing or subletting
           (whether or not consented to by the Lessor and whether under the
           provisions of Section 5.6.1 or otherwise) shall not relieve the
           Lessee named herein of any of the obligations of the Lessee under
           this Indenture of Lease. Therefore, the Lessee shall remain fully and
           primarily liable for all payments, as and when due, required under
           this Indenture of Lease as well as for the performance of all
           obligations of the Lessee hereunder.

           The liability of the Lessee and of such assignee (or sublessee or
           subtenant, as the case may be) shall be, and shall remain, joint and
           several.

           Further, and notwithstanding the foregoing, the provisions hereof
           shall not constitute a recognition (by way of substitution) of the
           assignment or of the assignee or sublessee or subtenant thereunder.
           At the option of the Lessor, upon the termination of the Lease
           established by this Indenture, any said assignment or sublease or
           subletting shall be terminated.

       (B) As additional rent, the Lessee shall promptly reimburse the Lessor
           for reasonable out of pocket, legal and other expenses incurred by
           Landlord in connection with any request by the Lessee for consent to
           any proposed assignment or sublease or subletting.

       (C) Any consent by the Lessor to an assignment or subleasing or
           subletting under any of the provisions of Sections 5.6.1 or 5.6.3
           shall not be consent to any other or future assignment or subleasing
           or subletting; - and shall not in any way be construed to relieve the
           Lessee from the obligation of obtaining the express consent in
           writing of the Lessor to any further assignment or subletting.

                                       30
<PAGE>
 
5.7  Indemnification: - Insurance

     (A)  Indemnification:

          The LESSEE covenants and agrees to defend with counsel first approved
          by LESSOR (which approval shall not be unreasonably withheld or
          delayed) and to save harmless, and indemnify the LESSOR from any
          liability for injury, loss, accident or damage to any person or
          property and from any claims, actions, proceedings and expenses and
          costs in connection therewith (including without limitation reasonable
          counsel fees) - - which injury, loss, accident, damage claims actions,
          proceedings and expenses and costs:-

          (a)  shall arise from, or are claimed to have arisen, from

                    (i)  the omission, fault, willful act, negligence or other
                         misconduct of the Lessee or of the Lessee's
                         contractors, licensees, invitees, agents, independent
                         contractors or employees; or

                    (ii) any use made or thing done or occurring on the premises
                         leased hereunder after the date that possession of the
                         said premises is first delivered to Lessee and until
                         the end of the Lease Term or extensions thereof; and
                         thereafter, so long as the Lessee shall be in occupancy
                         of any part of the Premises; provided, however, that
                         said use, activity or occurrence shall not be due to
                         the omission, fault, willful act, negligence or other
                         misconduct of the Lessor or its contractors, agents or
                         employees; or


          (b)  shall result from the failure of the Lessee to perform and
               discharge any of its covenants and obligations under this Lease.

          (c)  In the event that any said occurrence shall in part be due to, or
               in part caused by, the fault or negligence of LESSOR, the
               liability of, and indemnification by, the LESSEE hereunder shall
               be delimited only to the extent of the relative degree or
                            ----
               proportion of fault of the LESSOR in causing or contributing to
               said occurrence. In the event that said occurrence shall, in
               part, be due to the fault or negligence of the Lessor, the Lessee
               shall be liable to the Lessor and shall indemnify the Lessor to
               the degree or extent of the fault or negligence of the Lessee.

     (B)  INSURANCE

          The Lessee, further, covenants and agrees to maintain, with
          responsible companies qualified to do business, and in good standing,
          in Massachusetts, commercial general liability insurance or
          comprehensive general liability insurance with a broad form
          comprehensive liability endorsement covering the premises leased
          hereunder insuring the LESSOR (as an additional insured) as well as
          the Lessee with limits which shall, at the commencement of the Term,
          be at least equal to those stated in Section 1.1; and from time to
          time during the

                                       31
<PAGE>
 
      Term, shall be for such higher limits, if any, as are customarily carried
      in Greater Boston with respect to similar properties or which may
      reasonably be required by the LESSOR. Further, the Lessee shall maintain
      workmen's compensation insurance with statutory limits covering all of the
      employees of the LESSEE working in the premises leased hereunder.

      The Lessee shall deposit with Lessor on or before the Commencement Date
      and concurrent with all renewals thereof, certificates for such insurance
      designating the Lessor as insured, as above provided, and bearing the
      endorsement that the policies will not be canceled until after thirty (30)
      days' written notice to Lessor.
      
      In addition to the commercial general liability insurance (designating the
      Lessor as an additional insured), as above stipulated, the Lessee shall
      maintain and carry, at its expense, an insurance policy or contract
      insuring or indemnifying the Lessor (or the mortgagees of the Lessor, as
      their interests may appear) against loss of rental income (as established
      under this Lease) that may result or be caused by fire or other casualty
      to the premises to the premises leased hereunder. Said insurance shall
      insure or indemnify the Lessor (or its mortgagees) for a period of no less
      than twelve (12) months from and after the date of such fire, loss, damage
      or other casualty.

5.8   Furnishings, etc. of the Lessee at Lessee's Risk

      It is herewith agreed that all of the furnishings, fixtures, equipment,
      effects and property of every kind, nature and description of the Lessee
      and of all persons claiming by, through or under the Lessee which, during
      the continuance of this Lease or any occupancy of the Premises by the
      Lessee or anyone claiming under the Lessee, may be on the Premises or
      elsewhere in the Facilities or Complex, shall be at the sole risk and
      hazard of the Lessee; - and if the whole or any part thereof shall be
      destroyed or damaged by fire, water or otherwise, or by the leakage or
      bursting of water pipes, steam pipes, or other pipes, by theft or from any
      other cause, no part of said loss or damage is to be charged to or be
      borne by the Lessor; - except that LESSOR shall not be indemnified or held
      harmless or exonerated from any liability to the Lessee or to any other
      person, for any injury, loss, damage or liability that shall have been
      caused by the negligence or fault of the Lessor.

5.9   Right of Entry

      The Lessee agrees to permit Landlord and its agents to examine the
      premises leased hereunder at reasonable times and to require that the
      Lessee make any repairs or replacements for the proper maintenance and
      upkeep of the building and of the premises leased hereunder. Further, the
      Lessor may remove at the expense of the Lessee, any alterations,
      additions, signs, curtains, blinds, shades, awnings, aerials, flagpoles,
      or the like not consented to in writing.

      The Lessor may enter the premises, at reasonable times, to show the
      building and the premises to prospective tenants during the twelve (12)
      months preceding expiration of the initial Term or expiration of any
      extended term. Further, the Lessor may enter into and upon any part of the

                                      32
<PAGE>
 
      premises leased hereunder, at all reasonable times, for the purpose of
      showing same to prospective purchasers and mortgagees. (All persons must
      sign the log book upon entering the premises and note the time upon
      exiting the same.)

5.10  Floor Load: Prevention of Vibration and Noise

      The Lessee agrees not to place a load upon the Premises exceeding an
      average rate of 200 pounds of live load per square foot of floor area
      (partitions shall be considered as part of the live load); and not to move
      any safe, vault or other heavy equipment in, about or out of the Premises
      except in such manner and at such time as the Lessor shall, in each,
      instance authorize.

      Notwithstanding the foregoing, the LESSEE shall not place any load upon
                                                      ---
      the said Premises which will damage same, or which may cause damage
      thereto, even though said load shall be less than 200 pounds of live load
                                              ----
      per square foot of floor space. LESSEE agrees, therefore, that it shall
      not place any load upon or in said premises which will or may damage same.

      The weight limitation above set forth (200) pounds of live load per square
      foot) shall be adjusted downword in the event that the engineers the
      Lessor shall determine that said limitation of weight is excessive and
      requires adjustment downwards under the circumstances of the building. The
      Lessee agrees to assent to said reduction of weight limitation by said
      engineers as they shall determine.

      The Lessee agrees that business machines and mechanical equipment which
      cause vibration or noise that may be transmitted to the structure of the
      building leased hereunder shall be installed, maintained and used by the
      Lessee in such manner as to eliminate such vibration or noise.

5.11  Personal Property Taxes

      The Lessee agrees to pay promptly when due all taxes which may be imposed
      upon personal property upon the premises herein leased (including, without
      limitation, fixtures and equipment) to whomever assessed.

5.12  Compliance with Laws

      a.  The Lessee agrees to comply, and shall comply with, all applicable
          Legal Requirements now or hereafter in force which shall impose a duty
          on the Lessee or the Lessee relating to, or as a result of, the use or
          occupancy of the premises leased hereunder; - provided that Lessee
          shall not be required to make any alterations or additions to the
          structure, roof, exterior and load bearing walls, foundation,
          structural floor slabs and other structural elements of the Buildings
          unless the same are required by such Legal Requirements as a result of
          or in connection with use or occupancy by the Lessee of the premises
          leased hereunder. The Lessee shall promptly pay all fines, penalties
          and damages that may arise out of or be imposed because of its failure
          to comply with the provisions of this Section 5.12.

                                      33
<PAGE>
 
      b.  Not in limitation of the foregoing, the LESSEE shall conduct and carry
          on its activities within the Premises in accordance with all and any
          permits or licenses (wherever any said permit or license shall be
          required) properly applied for and issued by any and all governmental
          authority having jurisdiction or responsibility over same.

      c.  The LESSEE shall, at its sole expense, obtain and renew any and all
          permits or licenses necessary for the LESSEE to be or become a
          permitted user or permittee of the Waste Water Treatment Facility
          referred to in Section 1.14 and in Section 2.2.


5.13  Payment of Litigation Expenses

      The Lessee agrees to pay, as additional rent, all reasonable costs,
      counsel and other fees incurred by the Lessor in connection with the
      successful enforcement by the Lessor of any obligations of the Lessee
      under this Indenture of Lease.

                                  ARTICLE VI
                                  ----------
                                        
                              CASUALTY AND TAKING
                              -------------------
                                        
6.1   Fire and Casualty - Termination of Restoration; Rent Adjustment

      (A) Restoration - Termination

          If, during the initial or extended Term or Terms of the lease, the
          building leased hereunder (including the Site that affects the said
          leased premises) are damaged by fire or other casualty, and in the
          event that such fire or casualty damage cannot, in the ordinary
          course, reasonably be expected to be repaired within one hundred
          eighty (180) days from the time that repair work would commence,
          Lessor may, at its election, terminate this Lease by notice given to
          Lessee within sixty 60) days after the date of such fire or other
          casualty, specifying the effective date of termination. The effective
          date of termination specified by the Lessor shall not be less than
          thirty (30) days nor more than forty-five (45) days after the date of
          notice of such termination.

          If the LESSOR does not elect to terminate the Lease (in the event of
                             ---
          the foregoing), the LESSOR will proceed with due diligence to restore
          the premises to their condition prior to the fire or casualty.

      (B) Damage during Last Year

          If the said building and premises shall be damaged by fire or other
          casualty during the last year of the initial term or during the last
          year of each of the extended terms of the lease, and such fire or
          casualty damage cannot, in the ordinary course, reasonably be expected
          to be repaired within one hundred eighty (180) days from the time that
          said work would commence (and/or, as to special work or work which
          requires long lead time, then if such work cannot reasonably be
          expected to be repaired within such additional time as is

                                      34
<PAGE>
 
          reasonable under the circumstances given the nature of the work),
          then, in such event, the Lessee may, at its election, terminate this
          Lease by notice given to Landlord within sixty (60) days after the
          date of such fire or other casualty, specifying the effective date of
          termination. The effective date of termination specified by Tenant
          shall be not less than thirty (30) days nor more than forty-five (45)
          days after the date of notice of such termination.

      Unless terminated pursuant to the foregoing provisions, this Lease shall
      remain in full force and effect following any such damage; subject,
      however, to the following provisions.

      (C) Rent Adjustment in the Event of Temporary Displacement

          Notwithstanding the provisions of this Section 6.1, if the building
          leased hereunder shall be damaged by fire or casualty to such an
          extent that Lessee cannot operate in any reasonable portion thereof
          and, therefore, must temporarily shut down its usual operations in the
          building leased hereunder (for the reason that it is not reasonably
          tenantable for ninety (90) days or more), then Tenant shall have the
          right to seek other facilities until the said building shall be
          restored in accordance with the requirements of this Section 6.1. In
          the event that the provisions of the this Paragraph shall become
          applicable, the Annual Fixed Rent and additional rent shall abate from
          the date of the fire or other casualty giving rise to the
          applicability of this Paragraph until the Premises are so restored.
          Upon such restoration, Lessee shall return to the Premises and,
          commencing with the date the premises are so restored, the LESSEE
          shall resume paying Annual Fixed Rent and additional rent

      (D) Insurance Proceeds: Restoration

          In the event that the said building or the Premises or the Facilities
          (or Complex), or any part thereof; are damaged by fire or other
          casualty and, if this Lease is not terminated (pursuant to the
          provisions of the foregoing); or in the event that the Lessor or the
          Lessee shall have no right to terminate this Lease; --- provided that
          the holder of any mortgage (which includes the building leased
          hereunder to the Lessee as a part of the mortgaged premises) shall
          allow the net insurance proceeds to be applied to the restoration of
          the damaged building or the damaged Premises or Facilities, then, in
          such event, and promptly after such damage and after the determination
          of the net amount of insurance proceeds available, the Lessor shall
          use due diligence to restore the building or the Premises or the
          damaged Facilities, in the event of damage thereto, into proper
          condition for use and occupation.

          In such event, a fair and equitable part of the Annual Fixed Rent,
          proportionate and according to the nature and extent of the damage to
          the building shall be abated until the said building shall have been
          restored substantially to said proper condition for use and occupation
          by the Lessor; except for punch list items and long lead items.

          No portion of said insurance proceeds shall be applied to any damage
          or loss to any

                                      35
<PAGE>
 
          furniture, fixtures, apparatus or equipment belonging to, or installed
          by, or paid by, the Lessee.

          Said restoration by the Lessor (by means of the proceeds of insurance
          permitted to be so used by the holder of any mortgage upon the said
          Premises, as aforesaid), shall be completed within one (1) year from
          the date of the casualty or loss; provided, however, that said one (1)
          year period shall be extended in the event that any delay in
          completion of the restoration shall be due to causes beyond the
          reasonable control of the Lessor. In no event, however, shall the said
          extension be beyond eighteen (18) months beyond the date of the
          casualty or loss.

          In the event that said restoration shall not be substantially
          completed within said period or periods of time, the Lessee shall have
          the right to terminate this lease at any time after the expiration of
          such one (1) year period (or eighteen (18) months, as extended) until
          the restoration shall be substantially completed.

          Such termination shall take effect as of the thirtieth (30th) day
          after the date of receipt by Lessor of notice from the Lessee, with
          the same force and effect as if such date were the date originally
          established as the expiration date of this lease; provided, however,
          that if, within thirty (30) days after receipt by the Lessor of notice
          of said of termination from the Lessee, said restoration shall have
          substantially completed, then (in the event of such restoration), the
          notice of termination from the Lessee shall be of no force and effect;
          and this Lease and the Lease Term shall continue in full force and
          effect.

6.2   Loss Caused by Uninsured Risk

      Notwithstanding anything to the contrary contained in this Lease, if the
      building or Premises or the Facilities shall be substantially damaged by
      fire or casualty as the result of a risk not covered by the forms of
                                               ---
      casualty insurance at the time maintained by Lessor or by the LESSEE (with
      the LESSOR named as an insured or a loss payee), and such fire or casualty
      damage cannot, in the ordinary course, reasonably be expected to be
      repaired within ninety (90) days from the time that repair work would
      commence, the Lessor may, at its election, terminate the Term of this
      Lease by notice to the Lessee given within thirty (30) days after such
      loss. If the Lessor shall give such notice, then this Lease shall
      terminate as of the date of such notice with the same force and effect as
      if such date were the date originally established as the expiration date
      hereof.

6.3   Condemnation - Taking by Right of Eminent Domain

      In the event that there shall occur a taking by condemnation or by right
      of eminent domain, resulting in the taking of the entirety of the building
      leased hereunder, or if there shall occur a taking of such portion of the
      premises leased hereunder as to render the balance unsuitable for the
      purposes of the Lessee (even after reconstruction to the maximum extent
      practicable in the then circumstances), then, in such event, both the
      Lessor and the Lessee shall have the right to terminate this Lease by
      written notice to the other of its desire to do so; - provided that such
      notice shall be delivered not later than thirty (30) days after the Lessee
      shall have been deprived

                                      36
<PAGE>
 
      of possession. If either party shall give such written notice, then this
      Lease shall terminate as of the date of such notice with the same force
      and effect as if such date were the date originally established as the
      expiration date hereof.

      Further, if so much of the building leased hereunder shall be taken under
      said condemnation proceedings, as to render continued operation of the
      said buildings uneconomic (as a result of the said taking), both the
      Lessor and the Lessee shall have the right to terminate this Lease by
      giving notice to the other party of the desire of the party giving said
      notice to so terminate the lease, no later than thirty (30) days after
      LESSEE has been deprived of possession of the said Premises (or such
      portion thereof as may be taken). If either party shall give such notice,
      then this Lease shall terminate as of the date of such notice with the
      same force and effect as if such date were the date originally established
      as the expiration date hereof.

      In the event that

          (i)   any part of the premises leased hereunder be so taken or
                condemned during the initial Lease Term or any extension
                thereof, and

         (ii)   should, in such event, this Lease not be terminated in 
                                                  ---                         
                accordance with the foregoing provisions, and  

         (iii)  upon such occurrence, if provided that the holder of any
                mortgage (that includes the premises leased hereunder as part of
                the mortgaged premises) allows the net condemnation proceeds to
                be applied to the restoration of the Premises so taken or
                condemned,

                then, and in such event:-

                The Lessor agrees that, after the determination of the net
                amount of condemnation proceeds available to the Lessor, the
                Lessor shall use due diligence to put what may remain of the
                Premises into proper condition for use and occupation as nearly
                like the condition of the Premises prior to such taking as shall
                be practicable (excluding, however, any furniture, fixtures or
                                ---------              
                equipment of Tenant, or any other items installed or paid for by
                the Lessee).

                If the Premises shall be affected by any exercise of the power
                of eminent domain, then the Annual Fixed Rent and Lessee's share
                of real estate taxes shall be justly and equitably abated and
                reduced according to the nature and extent of the loss of use
                thereof suffered by Lessee.

6.4   Awards resulting from eminent domain takings

      The Lessor shall have, and hereby reserves, to itself any and all rights
      to receive awards made for damages to the premises leased hereunder, or to
      the Complex or to the Facilities (or any portion thereof) and, or with
      respect to the leasehold hereby created, which awards may result or accrue
      by reason of exercise of right of eminent domain, by condemnation
      proceedings pursuant thereto, or by reason of anything lawfully done in
      pursuance of public, governmental or other

                                      37
<PAGE>
 
      authority. The Lessee hereby grants, releases and assigns to the Lessor
      all rights of the Lessee to such awards. The Lessee covenants and agrees
      to execute and deliver such further instruments of assignments, with
      respect to said awards, and other assurances thereof as the Lessee may
      from, time to time request; - and if the Lessee shall fail to execute and
      deliver the same within fifteen (15) days after notice from the Lessor,
      the Lessee hereby covenants and agrees that the Lessor is, and shall be,
      irrevocably designated and appointed as its attorney-in-fact to execute
      and deliver in Lessee's name and behalf all such further instruments of
      assignments and other assurances thereof that shall conform with the
      provisions hereof.

      Nothing contained herein shall be construed to prevent the Lessee from
      prosecuting in any condemnation proceeding a claim for the value of any
      personal property or usual trade fixtures in the building or upon the
      Premises leased hereunder that belong to, or were installed by, the
      Lessee, or at the expense of the Lessee; or claims arising from the cost
      of relocation and moving; - provided, however, that such action, and any
      resulting award shall not affect or diminish the amount of compensation
      otherwise recoverable by Landlord from the taking authority.

                                  ARTICLE VII
                                  -----------
                                        
                                    DEFAULT
                                    -------
                                        
7.1   Default by the Lessee of its obligations under this lease: "EVENTS OF
      DEFAULT" by Lessee:  Remedies accruing to Lessor (Section 7.1)

      (A) The following occurrences or actions by the Lessee (listed hereinafter
          under Section 7.1(A) (I) through (iv) are, and shall constitute,
          "Events of Default", to wit: -

          (i)    The Lessee shall fail to pay the fixed RENT, additional rent or
                 other charges for which provision is made herein on or before
                 the date on which the same become due and payable, and the same
                 continues for ten (10) days after notice from Landlord thereof,
                 or

          (ii)   The Lessee shall neglect or fail to perform or observe any
                 other covenant herein contained required to be performed or
                 observed by the Lessee, and the Lessee shall fail to remedy the
                 same within thirty (30) days after notice to the Lessee
                 specifying such neglect or failure; or, if such failure be of
                 such a nature that the Lessee cannot reasonably remedy the same
                 within sixty (60) days, the Lessee shall fail to commence
                 promptly to remedy the same and to prosecute such remedy to
                 completion with diligence and continuity; or

          (iii)  The leasehold interest of the Lessee in the Premises shall be
                 taken on execution or by other process of law directed against
                 the Lessee; or

          (iv)   The Lessee: -

                 (a)  Shall make an assignment for the benefit of creditors, or
                      shall file a voluntary 

                                      38
<PAGE>
 
                      petition in bankruptcy; or
                 (b)  Shall be adjudicated bankrupt or insolvent; or
                 (c)  Shall file any petition or answer seeking any
                      reorganization, arrangement, composition, readjustment,
                      liquidation, dissolution or similar relief for itself
                      under any present or future Federal, State or other
                      statute, law or regulation for the relief of debtors; or
                 (d)  Shall seek or consent to or acquiesce in the appointment
                      of any trustee, receiver or liquidator of the Lessee or of
                      all or any substantial part of its properties; or
                 (e)  Shall admit in writing its inability to pay its debts
                      generally as they become due; or
                 (f)  A petition shall be filed against the Lessee in bankruptcy
                      or under any other law seeking any reorganization,
                      arrangement, composition, readjustment, liquidation,
                      dissolution, or similar relief under any present or future
                      Federal, State or other statute, law or regulation and
                      said petition shall remain undismissed for an aggregate of
                      sixty (60) days (whether or not consecutive), or
                 (g)  A debtor in possession, or a trustee, or a receiver, or a
                      liquidator of the Lessee of all or any substantial part of
                      its properties or of the premises leased hereunder, shall
                      be appointed with or without the consent or acquiescence
                      of the Lessee and such appointment shall remain unvacated
                      or unstayed for an aggregate of sixty (60) days (whether
                      or not consecutive).

      (B) In the Event of the Occurrence of any said "Events of Default" by the
          Lessee

          In the event that any of the said "Events of Default" shall occur, or
          if the Lessee shall commit any of the activity that shall constitute
          any of said "Events of Default", then, and in any of said cases
          (notwithstanding any license of a former breach of covenant or waiver
          of the benefit hereof or consent in a former instance), the Lessor
          lawfully may, immediately or at any time thereafter, and without
          demand or further notice, terminate this Lease by notice to the
          Lessee, specifying a date not less than ten (10) days after the giving
          of such notice on which this Lease shall terminate. This Lease shall,
          then, come to an end on the date specified therein as fully and
          completely as if such date were the date herein originally fixed for
          the expiration of the Lease Term (Lessee hereby waiving any rights of
          redemption); and the Lessee will then quit and surrender the Premises
          to the Lessor, but Lessee shall remain liable as hereinafter provided.

      (C) Entry by Lessor upon Such Termination

          If this Lease shall have been terminated as provided in this Article,
          then the Lessor may, without notice, re-enter the Premises, either by
          force, summary proceedings, ejectment or otherwise, and remove and
          dispossess the Lessee and all other persons and any and all property
          from the same, as if this Lease had not been made, and the Lessee
          hereby waives the service of notice of intention to re-enter or to
          institute legal proceedings to that end.

                                      39
<PAGE>
 
      (D) Responsibility of Lessee: Rent

          In the event that this Lease shall be terminated under any of the
          provisions contained in the Article VII (particularly, Section 7.1),
          or shall be otherwise terminated as a result of the breach by the
          Lessee of any of its obligations under this lease, the Lessee
          covenants and agrees that, in such case, the Lessee shall forthwith
          pay on the days originally fixed herein for the payment thereof,
          amounts equal to the several installments of rent and other charges
          reserved as they would, under the terms of this Lease, become due if
          this Lease had not been terminated or if the Lessee had not entered or
          re-entered, as aforesaid. The Lessee, in such case, shall pay, and
          shall be liable for, all said amounts whether the Premises be relet or
          remain vacant, in whole or in part, or for a period less than the
          remainder of the Term, or for the whole thereof. However, if the
          Premises shall be relet by the Lessor, the Lessee shall be entitled to
          a credit in the net amount of rent and other charges received by the
          Lessor as a result of said reletting, after deduction of all expenses
          incurred in reletting the Premises (including, without limitation,
          remodeling costs, brokerage fees and the like), and in collecting the
          rent in connection therewith, in the following manner:

          Amounts received by the Lessor, after reletting shall first be applied
          against such expenses incurred by the Lessor, until the all said
          expenses shall have been recovered; and until such recovery, the
          Lessee shall pay, as of each day when a payment would fall due under
          this Lease, the amount which the Lessee is obligated to pay under the
          terms of this Lease. When, and if, such expenses shall have been
          completely recovered, the amounts received from reletting by Lessor
          that shall not have been previously applied to recovery of said
          expenses, shall be credited against the obligations of the Lessee as
          of each day when a payment would fall due under this Lease. After said
          credit, the net amount of the said payments (in fulfillment of the
          obligations of the Lessee) shall be payable by the Lessee.

      (E) Liquidated Damages

          At any time after such termination, and whether or not Landlord shall
          have collected any damages pursuant to the foregoing, and at the
          election of the Lessor, the Lessee shall pay to the Lessor, as
          liquidated final damages and in lieu of all other damages beyond the
          date of notice from the Lessor to the Lessee, such sum that shall
          represent the amount of the excess, if any, of the total rent and
          other benefits, including payment of taxes, (which would have accrued
          to the Lessor under this Lease - from the date of giving of such
          notice through the expiration date of the then unexpired Lease Term -
          or extension thereof) -- over and above -- the then cash rental value
          (in advance) of the Premises for the balance of the said Lease term
          (or extension thereof)

      (F) Rights of Lessor upon Entry after an "EVENT OF DEFAULT"

          In case of any Event of Default, re-entry, dispossession by summary
                         ----- -- -------                                    
          proceedings or otherwise, the Lessee may

          (1)  re-let the Premises or any part or parts thereof; either in the
          name of the Lessor, or

                                      40
<PAGE>
 
          otherwise, for a term or for terms which may, at the option of the
          Lessor, be equal to, or less than, or exceed, the period which would
          otherwise have constituted the balance of the Term of this Lease; and
          may, further, grant concessions or free rent to the extent that Lessor
          considers advisable or necessary to re-let the same; and

          (2)  may make such alterations, repairs and decorations in the
          Premises as Landlord in its sole judgment considers advisable or
          necessary for the purpose of reletting the Premises. The making of
          such alterations, repairs and decorations shall not operate or be
          construed to release the Lessee from liability hereunder, as
          aforesaid. The Lessor shall in no event be liable in any way
          whatsoever for failure to re-let the Premises, or, in the event that
          the Premises are re-let, for failure to collect the rent under re-
          letting. The Lessee hereby expressly waives any and all rights of
          redemption granted by or under any present or future laws in the event
          the Lessee shall be evicted or dispossessed, or in the event that the
          Lessor shall obtain possession of the Premises in consequence of the
          violation by the Lessee of any of the covenants and conditions of this
          Lease whether said violation shall constitute an "Event of Default" or
          otherwise.

      (G) Remedies are Cumulative and not Exclusive upon Default

          The specified remedies to which the Lessor may resort hereunder are
          not intended to be exclusive of any remedies or means of redress to
          which the Lessor may, at any time, be entitled lawfully. The Lessor
          may invoke any remedy (including the remedy of specific performance)
          allowed at law or in equity as though specific remedies were not
          herein provided for. Further, nothing contained in this Lease shall
          limit or prejudice the right of the Lessor to file or enter a claim
          for its damages resulting from said termination of this lease, and
          obtain, in proceedings for bankruptcy or insolvency brought by or on
          behalf of the Lessee, an amount equal to the maximum allowed by any
          statute or rule of law in effect at the time when, and governing the
          proceedings in which, the damages are to be proved; whether or not the
          amount be greater, equal to, or less than the amount of the loss or
          damages referred to above.

7.2   Default by the Lessor of its Obligations under this Lease

      The Lessor shall in no event be in default in the performance of any of
      the obligations of the Lessor hereunder unless and until Lessor shall have
      failed to perform such obligations within thirty (30) days after notice
      from the Lessee to the Lessor properly specifying wherein Lessor has
      failed to perform any such obligation. In the event, however, that the
      default by the Lessor is of such nature as to require additional time
      (beyond said thirty (30) days), the time in which the Lessor shall be
      required to correct said default, shall be extended for a reasonable and
      commensurate time.

                                 ARTICLE VIII
                                 ------------
                                        
                           MISCELLANEOUS PROVISIONS
                           ------------------------

                                      41
<PAGE>
 
8.1  Extra Hazardous Use

     The Lessee covenants and agrees that the Lessee will not do, or permit
     anything to be done, in or upon the Premises, or bring in anything or keep
     anything therein, which shall increase the rate of any insurance that the
     Lessor shall maintain in respect to the Premises or the Facilities or the
     Complex above the standard rate applicable to the said premises for
     occupancy and use for the purposes (and use) to which the Lessee has agreed
     to devote and occupy the Premises. Further, the Lessee agrees that, in the
     event that the Lessee shall cause an increase to the Lessor in the rate of
     said insurance, the Lessee will promptly pay to the Lessor, within thirty
     (30) days after demand, any such increase resulting therefrom; which shall
     be due and payable as additional rent. The Lessor shall give notice to the
     Lessee of any such increase promptly after the Lessor shall receive
     knowledge of the same; provided that the Lessee shall be responsible for
     any such increases applicable to both the period prior to and after any
     such notice.

8.2  Waiver

     Failure on the part of the Lessor or the Lessee to complain of any action
     or non-action on the part of the other, no matter how long the same may
     continue, shall never be a waiver by the Lessor or by the Lessee,
     respectively, of any of their respective rights hereunder. Further, no
     waiver at any time of any of the provisions hereof by the Lessor or by the
     Lessee shall be construed as a waiver of any of the other provisions
     hereof; and a waiver at any time of any of the provisions hereof shall not
     be construed as a waiver at any subsequent time of the same provisions. The
     consent or approval of the Lessor or of the Lessee to or of any action by
     the other requiring such consent or approval shall not be construed to
     waive or render unnecessary the consent (or approval to) of the Lessor or
     of the Lessee to or of subsequent similar act by the other.

     No payment by the Lessee, or acceptance by the Lessor, of a lesser amount
     than shall be due from the Lessee to the Lessor shall be treated otherwise
     than as a payment on account. The acceptance by Lessor of a check for a
     lesser amount with an endorsement or statement thereon, or upon any letter
     accompanying such check, that such lesser amount is payment in full, shall
     be given no effect, and the Lessor may accept such check without prejudice
     to any other rights or remedies which the Lessor may have against the
     Lessee.

8.3  Cumulative Remedies
  
     The specific remedies to which the Lessor may resort under the terms of
     this Lease are cumulative and are not intended to be exclusive of any other
     remedies or means of redress to which such party may be lawfully entitled
     in case of any breach or threatened breach by the Lessee of any provisions
     of this Lease. In addition to the other remedies provided in this Lease,
     the Lessor shall be entitled to the restraint by injunction of the
     violation or attempted or threatened violation of any of the covenants,
     conditions or provisions of this Lease or to a decree compelling specific
     performance of any such covenants, conditions or provisions.

8.4  Quiet Enjoyment  

                                       42
<PAGE>
 
     If the Lessee shall perform all of the obligations of the Lessee under this
     Lease (including, but not limited to, payment of the rent and observing,
     keeping and performing all of the terms and provisions of this Lease to be
     observed, kept and performed by the Lessee), then, in such event, the
     Lessee shall lawfully, peaceably and quietly have, hold, occupy and enjoy
     the Premises during the initial Term (and any extension thereof), without
     hindrance or ejection by any persons lawfully claiming under the Lessor to
     have title to the Premises superior to the Lease, subject, however, to the
     terms of this Lease. The foregoing covenant of quiet enjoyment is in lieu
     of any other covenant, express or implied. It is understood and agreed that
     this covenant and any and all other covenants of the Lessor contained in
     this Lease shall be binding upon the Lessor and its successors only with
     respect to breaches that shall occur during the respective ownership of the
     interest of the Lessor by the Lessor or by the successors to or of the
     Lessor, as the case may be.
     
8.5  Notice to Mortgagee and Ground Lessor

     After receiving notice from any person, firm or other entity that it holds
     a mortgage which includes the Premises as part of the mortgaged premises,
     or that it is the ground Landlord under a lease with the Lessor, as ground
     Lessee or ground Tenant, which includes the Premises as a part of the
     demised premises, no notice from the Lessee to the Lessor shall be
     effective unless and until a copy of the same is given to such holder of a
     mortgage or ground Landlord; and the curing of any of defaults committed by
     the Lessor hereunder by such mortgage holder or ground Landlord within a
     reasonable time thereafter (including a reasonable time to obtain
     possession of the premises if the mortgagee or ground Landlord elects to do
     so) shall be treated as performance by Lessor hereunder. For the purposes
     of this Section 8.5 or Section 8.15, the term "mortgage" shall include a
     mortgage on a leasehold interest of the Lessor (but not one on leasehold
     interest of the Lessee).

8.6  Assignment of Rents

     With reference to any assignment by the Lessor of the interest of the
     Lessor in this Lease, or the rents payable hereunder, conditional in nature
     or otherwise, which assignment is made to the holder of a mortgage or
     ground lease on property which includes the Premises, the Lessee agrees, as
     follows: -

           (A) That the execution of said assignment by the Lessor, and the
               acceptance thereof by the holder of such mortgage or the ground
               Landlord, shall never be treated as an assumption by such holder
               or ground Landlord of any of the obligations of Lessor hereunder,
               unless such holder, or ground Landlord, shall, by notice sent to
               the Lessee, specifically otherwise elect; and

           (B) That, except as aforesaid, such mortgage holder or ground
               Landlord shall be treated as having assumed the obligations of
               the Lessor hereunder only upon foreclosure of such holder's
               mortgage and the taking of possession of the Premises, or, in the
               case of a ground Landlord, the assumption of the position of

                                       43
<PAGE>
 
               the Lessor by such ground Landlord.

           (C) The Lessor reserves, and shall have, the unrestricted right and
               power to grant mortgages with the premises herein leased as
               security under said mortgage. Further, the Lessor shall have the
               unrestricted right and power to make any assignment of the rents
               or benefits (in whole or in part) to any lender or third party
               accruing to the Lessor under this lease, with or without a
               mortgage conveyance.

8.7  Surrender

     No act or thing done by the Lessor during the Lease Term (or extension
     thereof) shall be deemed an acceptance of a surrender of the Premises, and
     no agreement to accept such surrender shall be valid, unless in writing
     signed by the Lessor. No employee of the Lessor or any agents of the Lessor
     shall have any power to accept the keys of the Premises prior to the
     termination of this Lease. The delivery of keys to any employee of the
     Lessor or to agents of the Lessor shall not operate as a termination of the
     Lease or a surrender of the Premises.

8.8  Brokerage

     (A) The Lessee warrants and represents that the Lessee has not dealt with
         any broker in connection with the consummation of this Lease other than
                                                                      ----------
         the Recognized Brokers designated in Section 1.7 hereof. In the event
         -------------------------------------------------------              
         any claim is made against the Lessor relative to dealings by the Lessee
         with brokers other than the Recognized Brokers designated in Section
         1.7 hereof, the Lessee shall defend the claim against the Lessor with
         counsel selected by the Lessee that shall, however, first be approved
         by the Lessor (which approval will not be unreasonably withheld); and
         the Lessee shall save harmless and shall indemnify Lessor on account of
         loss, cost or damage which may arise by reason of such claim.

     (B) The Lessor warrants and represents that the Lessor has not dealt with
         any broker in connection with the consummation of this Lease other than
                                                                      ----------
         the Recognized Brokers designated in Section 1.7 hereof; and in the
         -------------------------------------------------------   
         event any claim is made against the Lessee relative to dealings by the
         Lessor with brokers other than the Recognized Brokers designated in
         Section 1.7 hereof, the Lessor shall defend the claim against the
         Lessee with counsel of selected by the Lessor; - and the Lessor shall
         save harmless and indemnify the Lessee on account of loss, cost or
         damage which may arise by reason of such claim.

     (C) The Lessor shall be solely responsible for the payment of brokerage
         -------------------------------------------------------------------
         commissions to the Recognized Brokers designated in Section 1.1 hereof.
         ---------------------------------------------------------------------- 

8.9  Invalidity of Particular Provisions

     If any term or provision of this Lease, or the application thereof to any
     person or circumstance shall, to any extent, be invalid or unenforceable,
     the remainder of this Lease, or the application of

                                       44
<PAGE>
 
     such term or provision to persons or circumstances other than those as to
     which it is held invalid or unenforceable, shall not be affected thereby,
     and each term and provision of this Lease shall be valid and be enforced to
     the fullest extent permitted by law.

8.10 Provisions Binding, Etc.

     The obligations of this Lease shall run with the land, and except as herein
     otherwise provided, the terms hereof shall be binding upon and shall inure
     to the benefit of the successors and assigns, respectively, of the Lessor
     and of the Lessee (and, if Lessee shall be an individual, upon and to his
     heirs, executors, administrators, successors and assigns). Each term and
     each provision of this Lease to be performed by the Lessee shall be
     construed to be both a covenant and a condition. The reference contained to
     successors and assigns of the Lessee is not intended to constitute, and
     shall not constitute, a consent to subleasing or subletting or assignment
     by the Lessee.

8.11 Recording

     This Indenture of Lease shall not be recorded.

     The Lessee agrees not to record the within Lease; but each party hereto
                       ---
     agrees, on the request of the other, to execute a so-called Notice of Lease
     in form recordable and complying with applicable law and reasonably
     satisfactory to the attorneys of the Lessor and of the Lessee. In no event
     shall such document set forth rent or other charges payable by Lessee under
     this Lease; and any such document shall expressly state that it is
     executed pursuant to the provisions contained in this Lease, and is not
     intended to vary the terms and conditions of this Lease.

8.12 Notices

     Whenever, by the terms of this Lease, notice shall or may be given or
     delivered either to the Lessor or to the Lessee, such notice shall be in
     writing and shall be sent by registered or certified mail, postage prepaid,
     as follows:-

         If intended for the Lessor, it shall be addressed to the Lessor at the
         address set forth under Section 1.2.1 of this Indenture of Lease (or to
         such other address or addresses as may from time to time hereafter be
         designated by the Lessor) with a copy to the Lessor, Care of and
         Attention to its General Counsel, Frank N. Dardeno, Esquire, 424
         Broadway, Somerville, Massachusetts 02145).

         If intended for the Lessee, addressed to the Lessee, at 500 Arsenal
         Street, Watertown, Massachusetts 02172, Attention: George Hrono, Senior
         Vice President (or to such other address or addresses as may from time
         to time hereafter be designated by the Lessee by like notice), with a
         copy thereof to the then General Counsel of the Lessee (as designated
         by the Lessee) and, if the Lessor shall so elect, to the General
         Manager or Officer in Charge of the Lessee at the premises leased
         hereunder to the Lessee.

                                       45
<PAGE>
 
     Except as otherwise provided herein, all such notices shall be effective
     when received; provided that

       (i)  if receipt is refused, notice shall be effective upon the first
            occasion that such receipt is refused or
       (ii) if the notice is unable to be delivered due to a change of address
            of which no notice was given, then, in such event, notice shall be
            effective upon the date such delivery was attempted.

8.13 When Lease Becomes Binding

     Employees or agents of the Lessor have no authority to make or agree to
     make a lease or any other agreement or undertaking in connection herewith.
     The submission of this document for examination and negotiation does not
     constitute an offer to lease, or a reservation of, or option for, the
     Premises. This document shall become effective and binding only upon the
     execution and delivery hereof by both the Lessor and the Lessee. All
     negotiations, considerations, representations and understandings between
     the Lessor and the Lessee are incorporated herein and may be modified or
     altered only by written agreement between the Lessor and the Lessee. No act
     or omission of any employee or agent of the Lessor or of the Lessee shall
     alter, change or modify any of the provisions hereof unless said act or
     omission shall, in each instance, be specifically authorized, in writing,
     by the Lessor or the Lessee (as the case may be).

8.14 Section Headings

     The headings of the Sections as well as the titles of the Articles
     throughout this Lease are for convenience and reference only, and the words
     contained therein shall in no way be held to explain, modify, amplify or
     aid in the interpretation, construction or meaning of the provisions of
     this Lease.

8.15 Rights of Mortgagee

       This Lease shall be subject and subordinate to any mortgage now or
     hereafter on the Premises (the premises leased hereunder) or the Facilities
     or the Complex, and to each advance made, or hereafter to be made, under
     any mortgage, and to all renewals, modifications, consolidations,
     replacements and extensions thereof and all substitutions therefor;
     provided that the holder of such mortgage agrees to recognize the rights of
     ---------------------------------------------------------------------------
     the Lessee under this Lease (including the right to use and occupy the
     ---------------------------
     Premises) upon the payment of rent and other charges payable by the Lessee
     under this Lease and the performance by the Lessee of the obligations of
     the Lessee hereunder.

       In confirmation of such subordination and recognition, the Lessee shall
     execute and deliver promptly such instruments of subordination and
     recognition as such mortgagee may reasonably request.

                                       46
<PAGE>
 
        In the event that any mortgagee or its respective successor in title
     shall succeed to the interest of the Lessor, then, this Lease shall
     nevertheless continue in full force and effect and the Lessee shall attorn
                                                                         ------
     (and does hereby agree to attorn) to such mortgagee or successor; and to
                               ------
     recognize such mortgagee or successor as its landlord.


        With respect to any mortgage (which includes the Premises) that has been
     executed and recorded prior to the date of this Lease, if the holder of
                           -----
     said mortgage shall so elect, this Lease and the rights of Lessee
     hereunder, shall be superior in right to the rights of such holder, with
                         --------
     the same force and effect as if this Lease had been executed, delivered and
     recorded, or a statutory Notice thereof recorded, prior to the execution,
     delivery and recording of any such mortgage. The election of any such
     holder shall become effective upon either notice from such holder to the
     Lessee (which notice shall be given in the same fashion as notices from the
     Lessor to the Lessee are to be given hereunder) or by the recording in the
     appropriate registry or recorder's office of an instrument in which such
     holder subordinates its rights under such mortgage to this Lease.

        If in connection with obtaining financing for the Premises (the premises
     leased hereunder) or the Complex or Facilities, a bank, insurance company,
     pension trust or other institutional lender shall request reasonable
     modifications in this Lease as a condition to such financing, the Lessee
     will not unreasonably withhold, delay or condition its consent thereto;
     provided that such modifications do not increase the monetary obligations
     of the Lessee hereunder or materially adversely affect the leasehold
     interest hereby created.

8.16 Status Report

     Recognizing that both parties may find it necessary to establish to third
     parties (such as accountants, banks, mortgagees or the like), the then
     current status of performance hereunder, either party, on the request of
     the other made from time to time, will promptly furnish to the Lessor, or
     the holder of any mortgage encumbering the Premises or the Complex or the
     Facilities, or to the Lessee, as the case may be, a statement of the status
     of any matter pertaining to this Lease, including, without limitation,
     acknowledgments that (or the extent to which) each party is in compliance
     with its obligations under the terms of this Lease. Any such statement
     delivered by the Lessee pursuant to this Section 8.16 may be relied upon by
     any prospective purchaser or mortgagee of the Premises or the Complex or
     the Facilities or any prospective assignee of any mortgagee of the
     Premises.

8.17 Self-Help

     If the Lessee shall, at any time, default in the performance of any
     obligation under this Lease, the Lessor shall have the right, but shall not
     be obligated, to enter upon the Premises and to perform such obligation
     notwithstanding the fact that no specific provision for such substituted
     performance by the Lessor is made in this Lease with respect to such
     default. In performing such obligation, the Lessor may make any payment of
     money or perform any other act.

       All sums so paid by the Lessor (together with interest at the rate of two
                                                                          -- ---
       and one-half percentage
       ------------           

                                       47
<PAGE>
 
     points over the then prevailing prime rate in Boston as set by Bank Boston,
                                                             ------------------
     successor to The First National Bank of Boston) and all costs and expenses
     ----------------------------------------------
     in connection with the performance of any such act by the Lessor, shall be
     deemed to be additional rent under this Lease and shall be payable to
     Landlord immediately on demand.

     The Lessor may exercise the foregoing rights without waiving any other of
     its rights and without releasing the Lessee from any of its obligations
     under this Lease.

8.18 Holding Over

     Any holding over by the Lessee after the expiration of the term of this
     Lease shall be treated as a tenancy at sufferance at double the rents and
     other charges herein (prorated on a daily basis) and shall otherwise be on
     the terms and conditions set forth in this Lease, as far as applicable;
     provided, however, that neither the foregoing nor any other term or
     provision of this Lease shall be deemed to permit the Lessee to retain
     possession of the Premises or hold over in the Premises after the
     expiration or earlier termination of the Lease Term.

8.19 Non-Subrogation

     Any insurance carried by either party with respect to the Premises or
     property therein or occurrences thereon shall, if it can be so written
     without additional premium or with an additional premium which the other
     party agrees to pay, include a clause or endorsement denying to the insurer
     rights of subrogation against the other party to the extent rights have
     been waived by the insured prior to occurrence of injury or loss. Each
     party, notwithstanding any provisions of this Lease to the contrary, hereby
     waives any rights of recovery against the other for injury or loss due to
     hazards covered by such insurance to the extent of the indemnification
     received thereunder.

8.20 Extension Option

 (A) Conditions

     Provided that at the time of exercise of the option to extend and at the
     commencement date of the extension option period -

      (i)   there exists no Event of Default (defined in Section 7.1); and
                         --                                               
      (ii)  this Lease shall then be in full force and effect; and
      (iii) the Lessee has neither assigned this Lease nor sublet the Premises;

       Then, if said three (3) conditions shall prevail, the Lessee shall have
       the right to extend the Term hereof upon all the same terms, conditions,
       covenants and agreements herein contained (except for the Annual Fixed
       Rent which shall be adjusted during the option period as herein below set
       forth) for two (2) periods of five (5) years as hereinafter set forth.
       The option period is sometimes herein referred to as the "Extended Term".

                                       48
<PAGE>
 
  (B) First Five (5) Year Extended Term
     
      If the Lessee desires to exercise the option to extend the Term for the
      first five (5) year extended term (commencing December 1, 2007 and ending
      November 30, 2012), then the Lessee shall deliver notice to the Lessor of
      the request of the Lessee for quotation by the Lessor of Ninety Five (95%)
      per centum of the annual fair market rent for the Premises as of the
      commencement date of the first extension period. Such quotation shall be
      based on the use of the Premises as comparable office space in the Boston
      North Suburban Market (hereinafter called the "Annual Market Rent").
      Within thirty (30) days after receipt by the Lessor of said notice from
      the Lessee requesting such a quotation, the Lessor shall notify the Lessee
      of the quotation of the Lessor of Ninety Five (95%) per centum of the
      Annual Market Rent. Said Ninety Five (95%) per centum of the Annual Market
      Rent, however, shall, in no event, be less than the Annual Fixed Rent for
      the last year of the Original or Initial Term. The Lessee shall deliver
      said notice to the Lessor of its request for quotation by the Lessor of
      Ninety-five (95%) per centum of the annual fair market rent not earlier
      than fifteen (15) months nor later than Twelve months prior to the
      expiration term of this lease.

      In order to exercise its rights hereunder, the Lessee, (and within fifteen
      (15) days after receipt by the Lessee of the quotation from the Lessor of
      Ninety Five (95%) per centum of the Annual Market Rent) shall give written
      notice to the Lessor that it exercises its option to extend the Term of
      this Lease; in which case the Term of this Lease shall be extended for an
      additional term of five (5) years upon all of the same terms, conditions,
      covenants and agreements contained in this Lease except that the Annual
      Fixed Rent shall be equal to Ninety Five (95%) per centum of the Annual
      Market Rent as quoted by Lessor; provided, however (and as aforesaid), in
      no event shall the Annual Fixed Rent payable during the Extended Term be
      less than the Annual Fixed Rent for the last year of the Original Term.
      Upon the giving of such notice, this Lease and the Lease Term hereof shall
      be extended, for the first five (5) year Extended Term, without the
      necessity for the execution of any additional documents, except the Lessor
      and Lessee agree to enter into an instrument in writing setting forth the
      Annual Fixed Rent for the Extended Term but the failure to so enter into
      such a written instrument shall not negate the exercise of the applicable
      option to extend. Upon the giving of such notice of extension as aforesaid
      all references herein to the Lease Term or the term of this Lease shall be
      construed as referring to the Lease Term, as so extended, unless the
      context clearly otherwise requires.

  (C) Second Five (5) Year Extended Term

      If the Lessee desires to exercise the option to extend the term of the
      Lease for a second five (5) year Term (commencing December 1, 2012 and
      ending November 30, 2017), the Lessee shall deliver written notice to the
      Lessor of its desire and intention to extend the term of the lease for
      said additional five (5) year term not earlier than fifteen (15) months
                                         ------------------------------------
      nor later than twelve months prior to the expiration of the first five (5)
      ----------------------------------
      year extended term. The same terms and conditions of this Indenture of
      Lease in force and effect during the initial ten (10) year term; and
      during the first five (5) year extended term of the lease shall apply and
      shall be in force and effect during the said second extended five (5) year
      term of this lease; except, however, that the
                          ------
     

                                       49
<PAGE>
 
      Annual Fixed Rent during the said second five (5) year term (commencing on
      December 1, 2012) shall be the then market rent, to wit, the "Annual Fixed
      Market Rent"), as hereinafter set forth.

      If the Lessee desires to exercise the option to extend this lease for the
      said second five (5) year term (commencing December 1, 2012 and ending
      November 30, 2017), then the Lessee shall give notice to the Lessor, as
      aforesaid, not earlier than fifteen (15) months nor later than twelve (12)
                     ----------------------------------------------------------
      months prior to the expiration of the first five (5) year extension of
      ------------
      this Lease, of the request of the Lessee for quotation by the Lessor of
      the annual fair market rent for the Premises as of the commencement date
      of the second five (5) year extension period. Such quotation shall be
      based on the use of the Premises as comparable office space in the Boston
      North Suburban Market (hereinafter called the "Annual Market Rent").
      Within thirty (30) days after receipt by the Lessor of said notice from
      the Lessee requesting such a quotation, the Lessor shall notify the Lessee
      of the quotation of the Lessor of the Annual Market Rent. Said Annual
      Market Rent, however, shall, in no event, be less than the greater of the
                                                   ----     
      Annual Fixed Rent for the last year of the Original or Initial Term or the
      last prior of the first five (5) year extended term of this lease.

      In order to exercise its rights hereunder, the Lessee, (and within fifteen
      (15) days after receipt by the Lessee of the quotation from the Lessor of
      the Annual Market Rent) shall give written notice to the Lessor that it
      exercises its option to extend the Term of this Lease; in which case the
      Term of this Lease shall be extended for an additional term of five (5)
      years upon all of the same terms, conditions, covenants and agreements
      contained in this Lease except that the Annual Fixed Rent shall be equal
      to Annual Market Rent as quoted by Lessee; provided, however (and as
      aforesaid), in no event shall the Annual Fixed Rent payable during the
      Extended Term be less than the greater of the Annual Fixed Rent for the
      last year of the Original or Initial Term or the last year of the first
      five (5) year extended term of this lease. Upon the giving of such notice,
      this Lease and the Lease Term hereof shall be extended, for the second
      five (5) year Extended Term, without the necessity for the execution of
      any additional documents, except that Landlord and Tenant agree to enter
      into an instrument in writing setting forth the Annual Fixed Rent for the
      said second five (5) year Extended Term; but the failure to so enter into
      such a written instrument shall not negate the exercise of the applicable
      option to extend. Upon the giving of such notice of extension as aforesaid
      all references herein to the Lease Term or the term of this Lease shall be
      construed as referring to the Lease Term, as so extended, unless the
      context clearly otherwise requires.

      Notwithstanding anything herein contained to the contrary, in no event
      shall the Lease Term hereof be extended after the expiration of the said
      second five (5) year Extended Term (to wit:- in no event shall this lease
      be extended beyond November 30, 2017).

(D)   Option Granted to Extend for Two Five (5) year Terms Only

      The Lessee is herewith granted the option to extend this lease for two
      five (5) year Extended Terms; said options to the lease for said two
      Extended Terms to be exercised in accordance

                                       50
<PAGE>
 
        with the provisions herein above stated; and upon the terms, rent and
        provisions therein stipulated. The LESSEE is granted no further or other
        options to extend this Lease by the foregoing terms and provisions

8.21    Lessee Shall Look Only to the Interest of the Lessor to the Premises
        herein Leased.

        The Lessee specifically agrees to look solely to then equity interest of
        the Lessor in the specific premises herein leased to the Lessee for
        recovery of any judgment from Landlord. It is specifically agreed upon
        that neither the Lessor (original or successor), nor any beneficiary of
        any Trust which shall hold the interest of the Lessor, and no Trustee of
        any said Trust shall ever be personally liable for any such judgment, or
        for the payment of any monetary obligation to the Lessee. The provision
        contained in the foregoing sentence is not intended to, and shall not,
        limit any right that the Lessee might otherwise have to obtain
        injunctive relief against the Lessor or the successors in interest to
        the Lessor; provided, however, that said action (or any action that may
                    --------
        be brought by the Lessee) shall not involve, entail, or result in, the
        personal liability of the Lessor (original or successor), or of any
        successor Trustee to the persons named herein as the Lessor, or of any
        beneficiary of any Trust of which any person holding the interest of the
        Lessor is Trustee; and provided that said action shall not require the
        Lessor, its successors in title, or its trustees, or beneficiaries of
        said Trust to respond in monetary damages from the assets of the Lessor
        other than the equity interest of the Lessor, aforesaid, in the specific
        -----
        premises herein leased to the Lessee (the Premises). In no event shall
        Lessor ever be liable to Lessee for any indirect or consequential
        damages suffered or claims by the Lessee from whatever cause.

8.21.1  The Trustees of Lessor and Beneficiaries Not Personally Liable.

        In the event the LESSEE shall recover any judgment against the LESSOR,
        said judgment may, and shall, be satisfied only and exclusively from the
        premises specifically leased to the LESSEE hereunder.. Neither the
        Trustees of the Trust holding the interest of the LESSOR nor the
        beneficiaries of said Trust (or any of them) shall be liable for, or
        shall have any personal liability or responsibility in respect to said
        judgment. The LESSEE agrees that it shall look only to the interest of
        the LESSOR in said premises leased hereunder; shall not seek to recover
        said judgment against the Trustees or the Beneficiaries in their
        individual capacities; and shall not look to any interest of the Lessor
        in any assets held or owned by the Lessor other than the premises herein
        specifically leased to the Lessee.

8.22    Late Payment

        If the Lessor shall not have received any payment or installment of rent
        on or before the date (the "Due Date") on which the same first becomes
        payable under this Lease, the amount of such payment or installment
        shall bear interest ten (10) days after the Due Date through and
                   --------  
        including the date such payment or installment shall be received by
        Landlord, at a rate equal to the lesser of
                                         ------    

                                       51
<PAGE>
 
       (I)  the rate announced by Bank Boston, successor to The First National
            Bank of Boston, from time to time as its prime or base rate (or if
            such rate is no longer available, a comparable rate reasonably
            selected by the Lessor), plus two percent (2%), or
       (ii) the maximum applicable legal rate, if any.

       Such interest shall be deemed additional rent and shall be paid by the
       Lessee to the Lessor upon demand.

8.23   Governing Law

       This Lease shall be governed exclusively by the provisions hereof and by
       the law of the Commonwealth of Massachusetts, as the same may from time 
       to time exist.

8.24   This Indenture of Lease comprises a total of 53 pages consisting of eight
       (8) ARTICLES (I through VIII); along with the following Exhibits:

       EXHIBIT A:  showing the premises lease hereunder.
       EXHIBIT B:  showing layout of future extension.
       EXHIBIT C:  Agreement dated May 19, 1997.

8.25   This Lease Conditional Upon Release of Premises by AMETEK

       As indicated in the Agreement between the parties, dated May 19, 1997
       (referred to in Section 1.1), the premises herein leased are part of the
       Facilities leased to AMETEK AEROSPACE PRODUCTS, INC. ("AMETEK"),
       successor to GENERAL ELECTRIC COMPANY, under an Indenture of Lease dated
       November 13, 1968. This Indenture of Lease with GENERAL SCANNING, INC.
       is, therefore, upon the express condition that said AMETEK shall have
       released to the Lessor from its Lease the premises herein described and
       intended to be leased to the Lessee (See Section 1.5). (The foregoing
       Section 8.25 is now moot.)

8.26   Counsel

       Each party has had its own and independent counsel prepare, review and
       revise this Indenture of Lease prior to its execution and delivery; and
       each party has relied on its own independent counsel in respect to this
       Lease. (Said counsel, Frederick C. Morse and Frank N. Dardeno, Sr., have
       initialed each page of each of the four counterparts of this Lease.)

8.27   Dispute Resolution

       The parties shall seek to resolve any disputes that may arise with
       respect to this Indenture of Lease in good faith negotiations. If,
       despite the best efforts of the parties, said dispute shall not be
       resolved, the parties shall not resort to litigation in the Courts unless
                                                                          ------
       and until resolution of said dispute shall have been sought by means of
           -----
       submission of said dispute to third party and

                                      52
<PAGE>
 
       disinterested arbitration proceedings.

This Indenture of Lease is EXECUTED as a sealed instrument in two or more
counterparts, each of which shall be deemed to be an original, as of this 15th
day of July, 1997.

            THE LESSOR:-             THE WILMINGTON REALTY TRUST

Witnesses:                           /s/ Rosemarie Stanieich
                                     ----------------------------------------
                                     Rosemarie Stanieich,         Trustee
[SIGNATURE ILLEGIBLE]
---------------------
                                     /s/ Claudia J. Cipullo
                                     ----------------------------------------
                                     Claudia J. Cipullo,          Trustee

[SIGNATURE ILLEGIBLE]
---------------------
                                     /s/ Joseph O. Branzetti, Jr
                                     ----------------------------------------
                                     Joseph O. Branzetti, Jr.     Trustee    


            THE LESSEE:-             GENERAL SCANNING, INC.


  Witnesses:                      By /s/ Charles D. Winston 
                                     ----------------------------------------
                                     Charles D. Winston, President
 
[SIGNATURE ILLEGIBLE]
---------------------
                                  By /s/ Victor Wooley
                                     ----------------------------------------
                                     Victor Wooley, Treasurer
[SIGNATURE ILLEGIBLE]
--------------------- 

                                      53
<PAGE>
 
                                   EXHIBITS
                                        


                                      TO
                                        


                              INDENTURE OF LEASE
                                        


PREMISES:  60 FORDHAM ROAD, WILMINGTON, MASSACHUSETTS
LESSOR:  THE WILMINGTON REALTY TRUST
LESSEE:  GENERAL SCANNING, INC.
DATE OF LEASE: JULY 15, 1997



EXHIBIT A - PLAN TO ACCOMPANY LEASE AGREEMENT (DATED SEPT 18, 1997)

EXHIBIT B - FUTURE LAYOUT PLAN (DATED SEPT 18, 1997)

EXHIBIT C - AGREEMENT DATED MAY 19, 1997(14 PAGES)
<PAGE>
 
                                   AGREEMENT
                                        
                                      to

                          IMPROVE AND LEASE PREMISES
                                        
This AGREEMENT (in fourteen pages - sections A through Q) is entered into as of
this nineteenth day of May, 1997 by and between: -

      THE WILMINGTON REALTY TRUST (hereinafter referred to as the LESSOR; and

      GENERAL SCANNING, INC. (hereinafter referred to as the LESSEE)

The parties, more particularly defined under Section B hereof ("PARTIES") agree
to enter into a triple net lease with respect to the premises hereinafter
described and upon the terms herein outlined. This agreement, however, is
subject to approval by the parties of the terms, covenants and provisions to be
incorporated in an Indenture of Lease; but said terms, covenants and provisions
shall be consistent with, and shall reflect, the stipulations hereinafter set
forth.

Said premises are, at present, leased to AMETEK AEROSPACE PRODUCTS, Inc.
("AMETEK") as successor to GENERAL ELECTRIC COMPANY (see Infra). The Premises
must, therefor, be surrendered by AMETEK. This agreement, accordingly, is
subject to, and conditional upon the release of said premises from said existing
lease.

The execution and delivery of this agreement shall constitute authorization from
each of the parties to initiate the activities required of them under the
provisions hereof.

A. BACKGROUND AND RECITATIONS

   1. LOCATION:

      The premises subject to this proposal (hereinafter, the "THE PREMISES")
      are part of the facilities located on Fordham Road, in Wilmington and
      North Reading, Middlesex County, Massachusetts

      The premises to be leased hereunder comprise Building No.2 (north of
      Buildings 1 and 1A) with land pertaining thereto as well as parking area
      to rear (abutting east side of building).

   2. TITLE:

      The titles to the said land are registered by decree duly entered in the
      Land Court of the Commonwealth of Massachusetts.

      The titles are shown on Certificates registered in the Middlesex South
      District of the Land Court in Cambridge (as to land in North Reading) and
      in the Middlesex North District of the Land Court (as to land in
      Wilmington).

                                                       EXHIBIT C
                                                          TO
                                                    INDENTURE OF LEASE
                                          (60 FORDHAM ROAD, WILMINGTON, MASS.)

                                       1
<PAGE>
 
      The premises are located in Wilmington. A small portion of the parking
      area to the rear the building may be located in North Reading

   3. OWNERSHIP

      a. Original Owner, Developer and Lessor of the premises:

         BARBO REALTY TRUST

      b. Present Owner:

         THE WILMINGTON REALTY TRUST - established under a Declaration of Trust
         dated September 7, 1973 registered in the Middlesex South Registry
         District as Document No.15729 and there noted on Certificate of Title
         No.142138; and registered, further, in Middlesex North Registry
         District as Document No.63541 and there noted on Certificate of Title
         No.19837.

     c. Transfer of titles to THE WILMINGTON REALTY TRUST

        Title to all of the land (and facilities) was transferred by BARBO
        REALTY TRUST to THE WILMINGTON REALTY TRUST by deeds dated September 10,
        1973

        Both BARBO REALTY TRUST and THE WILMINGTON REALTY TRUST have the same
        families as beneficiaries.

   4  TENANTS

      a.  Upon completion of their construction, the facilities were leased, in
          November, 1969, to GENERAL ELECTRIC COMPANY.

      b.  Thereafter (in or about 1974), GENERAL ELECTRIC COMPANY, subleased
          Building No.2 (the premises) to CONVERSE, Inc.

      c.  In June, 1984, the Lessor sold to GENERAL ELECTRIC COMPANY (pursuant
          to the terms of its lease) twelve acres of the site subject to
          reservation of rights of way and access, with the grant to G.E. of
          easements and rights of access to service pipes, wires, valves and
          other devices appurtenant to the Waste Water Treatment Facility and
          the Fire Protection Station, along with other relevant restrictions.
          The title thereto (subject to said rights and easements), was then
          transferred to CONVERSE, INC. by GENERAL ELECTRIC COMPANY.

      d.  CONVERSE then constructed its present building upon a portion of said
          land located in North Reading (at Fordham Road) south of Building 1
          and Building 1A.

                                       2
<PAGE>
 
          As indicated, the Lessor retained, and still retains, rights of way
          and access to the site; including right of way and use of access
          roadway from Concord Street.
 
      e.  Since August, 1989, AMETEK AEROSPACE PRODUCTS, INC. has occupied the
          facilities.

   5. RIGHT TO TRANSFER TO NEW TRUST:

      The Lessor reserves the right to transfer the title to the premises to a
      new Trust (with same beneficiaries as THE WILMINGTON REALTY TRUST) to
      establish a separate identity for the premises proposed to be leased to
      the Lessee.

      Lessee shall consent to said conveyance of title and the leasehold
      interests and rights thereunder of the Lessee shall be confirmed.

B. PARTIES:

        LESSOR:  THE WILMINGTON REALTY TRUST, c/o Frank N. Dardeno, 424
                   Broadway, Somerville, Massachusetts 02145 (see Section A, 3,
                 b above)
        LESSEE:  GENERAL SCANNING, INC., a Corporation existing under the
                   laws of the Commonwealth of Massachusetts, with its principal
                 offices located at 500 Arsenal Street, in Watertown,
                 Massachusetts 02172. 

C. PREMISES  The one story brick and concrete building known as Building no.2 of
             the facilities located at, and numbered as, 50 Fordham Road, in
             Wilmington, Massachusetts. Said building comprises about 78,000
             square feet of floor space (to be verified)

             Said premises will include the lot upon which said building was
             constructed and the parking area contiguous to the rear (or west)
             thereof; along with any open areas of land that may be appurtenant
             thereto in conformity with applicable zoning regulations

             The total of said land area (including the building site) shall be
             shown upon a plan of land prepared by the engineers of the Lessor;
             which plan shall be incorporated within the Indenture of Lease to
             define and delineate the leased premises.

             The Lessor reserves the right to lease the premises and the land
             appurtenant thereto to the Lessee without formal approval of the
             plan delineating the said premises as a Subdivision; provided that
             the lease of the premises shall be effective and valid.

                                       3
<PAGE>
 
             However, the Lessor may, at any time, present for approval a plan
             delineating the premises as a Subdivision (under the Subdivision
             Control Law); including designation of the premises as a
             condominium with participatory rights to the Waste Water Treatment
             Facility that services said premises.

D. TERM:     Ten (10) years - commencing December 1, 1997

E. RENT

      1.  BASE RENT:

          During said term, the base annual rent (due and payable in equal
          monthly installments) - calculated or determined on the basis of the
          square feet of floor space. - shall be, as follows:-

          a.  Years one through three  - at $5.00 per square foot (triple net);
          b.  Years four through seven - at $5.40 per square foot (triple net);
          c.  Years eight through ten  - at $5.80 per square foot (triple net).

      2.  ADDITIONAL RENT:

          Lessee shall, further, pay all operating costs as and when due -
          including, without limitation, real estate and other taxes assessed, 
          utilities, ground care, snow removal, maintenance, service or
          maintenance agreements (for HVAC or any other equipment or building
          elements), etc.

      3.  REIMBURSEMENT TO LESSOR OF ADVANCE:

          As hereinafter stated, the Lessor will make a one time payment to the
          Lessee, not to exceed $800,000.00, toward the renovations and
          improvement to be completed and to be paid for by the Lessee. The
          principal of said payment, along with all financing costs (including
          interest and carrying charges) incurred by Lessor to secure said
          funds, shall be reimbursed to the Lessor by the Lessee in monthly
          payments as additional rent. Said one time payment is upon the
          condition that the Lessor shall be granted a loan in said amount and
          for said purpose from a conventional banking institution and upon the
          terms hereinafter set forth under Paragraph G 2 b hereof.

F. RENOVATIONS and IMPROVEMENTS:

      1.  Responsibility for said Renovations and Improvements

       a.  Those to be completed at cost to LESSOR

           (1). Demolition of existing interior; and removal of connector/walk
                between

                                       4
<PAGE>
 
                Building 2 and Building lA (occupied by AMETEK).
           (2). Installation of new roof and roof insulation with replacement of
                decking and appurtenant structural elements wherever required..
                Said new roof insulation shall comply with building code
                requirements relative thereto.
           (3). Installation of new double pane glass throughout and new double
                pane glass in atrium or vestibule area; and repair of flooring
                in "computer" area.
           (4). New HVAC units.
           (5). New fire alarm system
           (6)  If the vinyl-asbestos in a small area of the building shall
                require removal, same shall be at Lessor's expense.
           (7)  Resurfacing of Parking Areas; delineation of parking spaces.
           (8)  The entrance to Building No.2 shall be "up-graded". The Lessor
                and the Lessee shall each pay one half of the cost thereof. Both
                of the parties shall approve the plans and total cost of the
                said improvement.

        B. THOSE TO BE COMPLETED AT COST TO LESSEE

           All other renovations and improvements whether fixtures to the
           building or preparation of interior for needs of the Lessee.

     2. COORDINATION OF RENOVATIONS AND IMPROVEMENTS ACTIVITIES 

        a. Parties shall coordinate their activities in completing the
           renovations and improvements. Said renovations and remodeling shall
           require the prior approval of the Lessor.
        b. Parties, through their engineers and representatives, will consult
           upon the various phases of the work to the end that the respective
           needs of the parties shall be satisfied and conflicts minimized.
        c. Not in limitation of above, Lessee shall be consulted with
           installation of HVAC units.

           More specifically, the Lessee shall have the right to design the HVAC
           system in order that same shall be in accordance with its
           requirements. However, the Lessee shall submit is plans,
           specifications and design for the HAVOC system to the LESSOR for its
           prior approval; which approval shall not be unreasonably withheld or
           delayed.

        d. Lessee shall furnish Lessor, for its prior approval, plans and
           architectural drawings for said renovations and remodeling; and,
           further, a copy of the contract entered into for same along with the
           bids.

       (e) Any sums due from the Lessor to the General Contractor engaged by the
           Lessee (Hoffman/Callahan) for work or improvements for which the
           Lessor is responsible

                                       5
<PAGE>
 
               (as set forth above in Section F,1,a) shall be paid by the Lessor
               to the Lessee within thirty (30) days after presentation of the
               invoice by said Contractor for said work or improvements.

           (f) Lessee shall pay, in a timely manner, its contractors, workmen
               and providers for all work and for all improvements for which the
               Lessee is responsible; and shall not permit any lien for said
               work or improvements to be placed against the premises either by
               workmen, suppliers, contractors or other providers.

G.   PAYMENT AND FINANCING OF RENOVATIONS AND IMPROVEMENTS 

       1.  RESPONSIBILITY WITH RESPECT TO RENOVATIONS AND IMPROVEMENTS:

           a.  Lessor will pay for those completed at its expense (set forth in
               Section F,1,a above);
           b.  Lessee shall be responsible, and pay for, all other construction
               and improvements.

       2   FINANCING

           a.  Lessee shall be solely responsible for the payment of all
               Renovations and Improvements (other than those listed above to be
               paid for by Lessor as set forth in Section F, 1, a); and Lessee
               shall pay for same directly.

           b.  Upon the commencement date of the Lease, the LESSOR shall make a
               one time payment to the Lessee toward said Renovations and
               Improvements in the maximum sum of $800,000.00; but only upon the
               following conditions:-

               (1) Said Renovations and Improvements shall benefit or improve
                   the building and its appurtenances and shall not be of a
                   special nature in furtherance of the business activities of
                   the Lessee.

               (2) The Lessor shall approve the renovations and improvements for
                   which it shall make payment to the Lessee; which approval by
                   the Lessor shall not be unreasonably withheld or delayed.

               (3) This reimbursement is effectuated to the Lessee in its need
                   to maintain a strong cash position and to accommodate the
                   Lessee. (The Lessee represents that the Renovations and
                   Improvements to be completed by the Lessee shall entail an
                   expenditure of about $1,700,000.00 and, in addition,
                   expenditures for fixtures and equipment).

               (4) The Lessor shall apply for a loan to finance said payment to
                   the Lessee (not to exceed $800,000.00) from a conventional
                   banking institution at current rates of interest in order to
                   enable the Lessor to make said one time payment; and the
                   obligation to make said payment to Lessee is subject to, and
                   upon the express prior condition, that said loan from said
                   banking institution shall be granted to the Lessor.

                   (a) Said loan shall be amortized for a term not exceeding ten
                       (10) years;

                                       6
<PAGE>
 
                   (b) The Lessee shall reimburse the Lessor for the entire cost
                       of said borrowing- including the principal of the loan,
                       interest thereon, finance and carrying charges, and all
                       and any other disbursements and expenses incurred by the
                       Lessee to effectuate said loan.

                       Transactional costs (including bank counsel fees and
                       origination fees) and any and all expenses incurred in
                       order to effectuate said loan or associated with said
                       borrowing shall be paid by the Lessee to the Lessor as
                       incurred.

                       All other payments necessitated by said loan shall be
                       reimbursed to the Lessor by the Lessee in the form of
                       increased monthly rent (added to the base rent and other
                       rent payments) to over the entire principal and interest
                       and all carrying charges.

               (5) To facilitate said borrowing by Lessor to make said payment
                   to Lessee, the Lessee shall provide to the lender its
                   guaranty for the payment of said loan if necessary.
               (6) Lessee shall make a good faith effort to secure a commitment
                   for said loan setting forth the terms thereof.
               (7) The obligation on the part of the Lessor to make said one
                   time payment to the Lessee (and to secure the loan therefor)
                   is upon the express condition that said payment to the Lessee
                   (and the repayment thereof) shall not result in any adverse
                   income tax consequence to the Lessor. In particular, the
                   parties agree that said payment (and the loan to effectuate
                   same) is upon the condition that the Lessor shall not thereby
                   incur any income or other federal or state taxes as result
                   thereof


H.   RESPONSIBILITIES 

       1.  MAINTENANCE

           a.  Upon completion of all the renovations and improvements, the said
               building and its appurtenances will be in prime condition with
               new insulated roof, structural replacements where needed, new
               mechanical elements, renovated and remodeled interior, new double
               pane glass throughout, paved parking area, etc.

           b.  All warrantees and guarantees issued by installers, contractors
               and suppliers shall be made available to, and benefit the Lessee.

           c.  The lessee shall be responsible for all maintenance of the
               interior of the building, paved areas, mechanical appurtenances,
               all roofing elements, HVAC units, and

                                       7
<PAGE>
 
               all other aspects of the building and its facilities.

           d.  The lease to be entered into shall be a triple net lease

           e.  Not in limitation of the foregoing (and unless revised by prior
               written stipulation or agreement of the parties), the Lessee
               shall be responsible for all interior elements of the building,
               including its mechanical components, all wiring (electrical or
               otherwise), all plumbing, all surfaces, flooring and any and all
               other appurtenances. Lessor shall, also, be responsible for
               maintenance of all windows, of the roof and its elements,
               cosmetic appearance and maintenance of the exterior, maintenance
               of all parking areas and the paved surface of said parking areas,
               all landscaping, and components of the building (as set forth
               above in Section H, 1, c.) Lessor shall turn over and assign to
               Lessee all warranties and guarantees from all suppliers,
               contractors, and workmen with respect to any improvements to the
               building and premises paid for by the Lessor.

               Lessor shall be responsible for the structural elements of the
               exterior of the building; as well as for apparatus, piping or
               wiring delivering utilities from the public way to the edge of
               the building

       2.  TAXES

               Lessee shall be responsible for all real estate and other taxes
               assessed by any government authority against the real estate
               (including building, land and improvements) leased to the Lessee

       3.  INSURANCE AND INDEMNIFICATION

           a.  Lessee, at its sole cost, will maintain fire and casualty loss
               insurance, insurance against liability for losses, damages or
               injury of any kind to anyone upon the premises, and coverage
               against all other insurable risks; and Lessee shall name the
               Lessor as an additional insured upon all said policies issued by
               recognized companies licensed to do business in Massachusetts.

           b.  Lessee shall indemnify and hold harmless the Lessor against any
               loss, claims or damages resulting from any of its activities; and
               shall promptly defend against claims resulting therefrom.

           c.  Lessee shall comply will all relevant laws and legal requirements
               and environmental regulations in the conduct of its operations.
               Lessee shall not expose Lessor to damages, loss or expense as a
               result of any activities of the Lessee - including, but not
               limited to, use of the premises, operations, discharges.

                                       8
<PAGE>
 
I. POSSIBLE EXPANSION

     Provided that said expansion shall be feasible, when requested, the Lessor
     will construct an expansion or extension (of not more than 40,000 square
     feet of floor space) to the east of the building if required by the Lessor
     (see K, 1, d below); subject, however, /to the following conditions:-

     1.  The Lessee shall be able to secure financing for said expansion from a
         conventional banking institution at then current rate of interest;
     2.  The expansion shall be permitted under all applicable laws and
         regulations - including zoning and building requirements
     3.  All required permits shall be issued -- including approvals from
         environmental regulatory agencies, state, federal (if necessary) and
         municipal authorities, and any other governmental body that may have
         oversight responsibilities.
     4.  The Lessor and the Lessee shall agree upon the rent, terms and
         conditions of the Lease affecting the present premises an said possible
         expansion.
     5.  The cost of moving pipes, tubes, wires, valves and any and all devices
         that now service the Waste Water Service Facility, the Fire Protection
         Station and any other support system for the buildings upon the site
         shall be an expense attributable to the construction costs of the said
         expansion; and shall be factored into the agreed upon rent.

         The obligation to construct said expansion is upon the condition that
         said devices can be moved; that the relevant easements and rights of
         way or access may be relocated along a new path; and that the easements
         and rights of way or access to service same shall be established and
         confirmed in their new path or location with the written consent of
         all parties that may have an interest therein.

     6.  The Lessee shall have the right to secure to provide the financing for
         said expansion if the Lessor shall be unable to secure same. In the
         event that the said expansion shall be financed by the Lessee, the base
         rent established for said expansion shall be adjusted to reflect any
         cost incurred by the Lessee with respect to said financing and shall be
         appropriately adjusted to said circumstances.

     Lessor shall secure from its engineers an opinion as to the feasibility of
     the expansion, as set forth under Section O, 4)

J. OPTION TO EXTEND LEASE

     Lessee shall have two successive options to extend the lease each for a
     term of five (5) years upon the same terms and conditions of the original
     ten (10) year term except that the base rent (see Section E. 1 above)
     shall be established, as follows:

                                       9
<PAGE>
 
         It is agreed that

           a.  With respect to the first of said two five (5) year option terms,
               the base rent shall be established during said five (5) years at
               the rate of ninety five (95%) percentum of the then market rent;

           b.  With respect the second of the said two (2) five year option
               terms, the base rent during said second five (5) year term shall
               be the then market rent.

K. SUBLEASING

         Lessee shall not sublease or sublet the premises or any portion thereof
         unless, in each in each instance, the Lessor shall have given its
         approval in writing to said sublease or subletting; which approval the
         Lessor shall not unreasonably withhold or unreasonably delay. In the
         event that the rent for said portion subleased or sublet shall exceed
         the rent paid to the Lessor, the increment shall be retained by the
         Lessee.

L. ENVIRONMENTAL - 21E -Etc.

     1.  The parties are aware that the site upon which the facilities are
         located has been under review by the Department of Environmental
         Protection ("DEP"); and that the former occupant, GENERAL ELECTRIC
         COMPANY ("G.E."), was named the responsible party in a Notice of
         Responsibility dated June 11, 1986. Subsequently, the Lessor received a
         Notice of Responsibility ("N.O.R.") from DEP dated April 16, 1991
         occasioned by bankruptcy proceeding instituted by the parent company of
         Converse, Inc. (Sublessee of G.E. of Building No.2.)

     2.  The contamination of the site resulted from releases of gasoline, oil
         and other substances by G.E. and its sub-lessee, Converse, Inc.

     3.  G.E. accepted and assumed the responsibility to conduct remediation
         activities in accordance with plans submitted to, and approved by, D.
         E. P. (including matters referred to in the N.O.R mailed to the Lessor
         dated, as stated, April 16, 1991 and occasioned by the bankruptcy
         proceedings aforesaid).This responsibility has been expressly
         acknowledged and assumed by the successors to G.E., i.e., MARTIN
         MARIETTA CORPORATION and its successor, LOCKHEED MARTIN CORPORATION
         ("LOCKHEED").

         LOCKHEED is committed to (and is engaged in) the necessary remediation
         process as approved by, and under the oversight of, D. E. P.

     4.  Lessor will seek reports of the engineers engaged by LOCKHEED. These,
         as well as

                                      10
<PAGE>
 
         progress reports relating to the remediation activities as received by
         the Lessor, shall be submitted by the Lessor to the Lessee.

     5.  LESSOR shall indemnify the Lessee from any claims arising out of any
         contamination of the site that has occurred prior to the occupancy of
         the leased premises by the Lessee; with the understanding that in the
         event any such claims shall arise, the Lessor shall make claim in
         respect thereto against the responsible party or parties (see above).
         Accordingly, in the event that any such claim shall arise, the Lessor
         with the cooperation of the Lessee, shall require intervention of, and
         indemnification from, the responsible party or parties, as above set
         forth, against any damages resulting from said claims. The Lessor and
         the Lessee shall consult and to co-operate with each other in the event
         that any such claims shall arise.

     6.  The parties acknowledge that the Lessor is currently engaged in
         negotiations with LOCKHEED with respect to the continuing
         responsibility of LOCKHEED (subject to the oversight of the D. E. P.)
         and to confirm and define liability, indemnification and the nature of
         related documentation and agreements that may be agreed upon. Lessee
         agrees to cooperate with respect thereto if requested in order that
         remediation activities shall continue and be facilitated to further the
         best interests of the parties.

M. EASEMENTS AND RIGHTS OF ACCESS

     Lessor shall retain existing easements and rights of way over the
     facilities and the premises (and to reserve additional easements and rights
     of access) in furtherance of its management obligations and oversight -
     including right to pass and re-pass and be and remain upon the premises to
     perform work upon, and to service, water and fire protection facilities and
     lines, Waste Water Treatment Facility, and for any other purpose required
     by the Lessor. Easements and rights of access have been granted for this
     purpose to AMETEK, as successor to G. E. Further, Lessor retains, and shall
     have, the right to grant easements in connection with said management and
     oversight (including easements to LOCKHEED MARTIN CORPORATION in order to
     facilitate its remediation of the site as required by D. E. P. - See
     Section L hereof).

     Said easements and rights of access shall not unreasonably interfere with
     the business activities of the Lessee.

N. WASTE WATER TREATMENT FACILITY

   1.  Said Building No.2 is serviced by a new and "state of the art" waste
       water service facility (placed on line within the last year) located
       northeast thereof. (Expected life of said facility - - about thirty 
       years -)

   2.  Lessor shall assume cost of providing service of said facility to Lessee,
       including costs

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<PAGE>
 
       of its operation and ordinary maintenance. Said costs shall be shared
       with the other tenant of the facilities, AMETEK AEROSPACE PRODUCTS, INC.
       (AMETEK); provided only, however, that in the event a replacement of the
       said facility (beyond maintenance and operation) the tenants using same
       shall be responsible for said replacement and shall contribute thereto
       upon the agreed upon formula.

       During the first ten (10) years of the term of the lease, however, Lessee
       shall have no responsibility with respect to replacement of the facility.



   3.  In the event that there shall be any damage, dysfunction or loss to the
       said Waster Water Treatment facility caused by any use, activities or
       misuse by the Lessee or any of its personnel, representatives or
       employees, the Lessee shall indemnify the Lessor with respect to said
       damage, dysfunction or loss and shall make the necessary payments to
       rectify said damage, dysfunction or loss

   4.  Lessee will pay that share of the real estate or other taxes assessed
       against said Waste Water Treatment Facility (in the event that any shall
       be assessed or levied in respect thereto) equivalent to the percentage of
       operational and management costs thereof attributable to the Lessee.

O. PLANS, EXHIBITS, ETC.

   1. Lessor shall furnish to Lessee

          (a) Plan designating the premises (see above C, "PREMISES")
          (b) Plan showing parking places;
          (c) Status of application for approval of driveway into the premises
              from Fordham Road along the northerly bound of the premises.
          (d) Lessor will request its engineers to indicate a preliminary
              outline on the subdivision or other plan the location of the
              expansion to Building No.2 referred to in Section H above
              ("POSSIBLE EXPANSION") and seek preliminary opinion as to its
              feasibility.

   2. LESSEE SHALL

      "Work out" with Ametek parking arrangement in the area along the south
      side (entrance of) the building.

      In the event that there may be common charges for any services to the
      premises, cost thereof will be shared on a percentage of use basis.

   3. AS TO WATER TOWER TO REAR OF BUILDING:

      (a) This facility services Building 1 and Building 1A occupied by Ametek

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      (b) Its maintenance is the responsibility of Ametek (who shall paint
          the water tower).
      (c) Lessor will request of its engineers and surveyors that said tower
          be left in the area of land that is occupied by Ametek in the
          formulation of the subdivision.
      (f) If, however, the tower shall remain upon any part of the premises
          leased to the lessee, all taxes assessed against said facility shall
          be paid by Ametek; and its operation and maintenance shall remain the
          responsibility of Ametek. In such event, Lessor shall retain right of
          access for benefit of Ametek

P. BROKERAGE: - shall be the responsibility of the Lessor

Q. MISCELLANEOUS

   MATTERS OF CONCERN TO AMETEK (TO BE ADDRESSED):

     1   Fire sprinklers - Ametek wishes connections to both P.1.V.'s be
         severed; with new feed line from street. (To avoid activating
         sprinklers, merely closing valves is not sufficient.)

     2   Ametek requires that the fire tank suppression system remain part of
         its sprinkler system. Requires natural gas feed from Building No.2.

     3   All shared electrical feeds to be segregated and metered separately.
         (Current underground feed to Building No.2 must be removed from main
         switch gear.)

     4.. Glass tunnel - connector. (AMETEK would like to discuss this)

     5.  Delineation of property lines (AMETEK would like to discuss this)

     6   Parking:

         (a) Shared parking between buildings;
         (b) Parking spaces pertaining to AMETEK and to Scanning should be
             differentiated with different colored lines.
         (c) Parking lot lighting is already separated and segregated.

     7.  AMETEK has closed the entrance from Concord Street to afford extra
         protection to parked vehicles. It will be kept open if General Scanning
         so requires.

     8.  AMETEK has a federal EPA permit to discharge non-contact cooling water
         through outsell. If General Scanning wishes to utilize this outsell for
         similar purposes, AMETEK must be informed so that request for a new
         permit may be filed.

     9.  Snow removal and Landscaping

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          AMETEK wishes to discuss arrangement for the service with General
          Scanning

      10. AMETEK will provide around-the-clock security for its facilities.
          General Scanning must provide security for its own facilities.

      11. Insurance.

          General Scanning will provide insurance for its facilities. (See H, 3
          above)

IN WITNESS WHEREOF, the parties have hereunto set their hands and seals as
of this nineteenth day of May, 1997.

                   THE WILMINGTON REALTY TRUST (Lessor)

                   /s/ Rosemarie Stanieich            
                   ---------------------------------------
                   Rosemarie Stanieich.            Trustee

                   /s/ Claudia J. Cipullo              
                   ---------------------------------------
                   Claudia J. Cipullo,             Trustee

                   /s/ Joseph O. Branzetti Jr.         
                   ---------------------------------------
                   Joseph O. Branzetti Jr.,        Trustee 
                   (Approved as to form:

                   /s/ Frank N. Dardeno, Sr.  
                   -------------------------------------------------------------
                   Frank N. Dardeno, Sr., Of counsel to Lessor)


                   GENERAL SCANNING, INC. (Lessee)

                   By /s/ Charles D. Winston                              6/3/97
                      ----------------------------------------------------------
                      Charles D. Winston, President and Chief Executive Officer


                   By /s/ George Hrono                                   5/30/97
                      ----------------------------------------------------------
                      George Hrono, Senior Vice President 
                      (Approved as to form:

                   /s/ Frederick C. Morse 
                   -------------------------------------------------------------
                   Frederick C. Morse, General Counsel to Lessee)

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