Exhibit 10.85

                            REVOLVING PROMISSORY NOTE

$3,000,000                                                      McLean, Virginia
                                                                  March 27, 1997

     FOR VALUE RECEIVED, VERSAR, INC., a corporation organized under the laws of
the State of Delaware and GEOMET  TECHNOLOGIES,  INC., a  corporation  organized
under the laws of the State of Delaware (collectively,  the "Borrowers" and each
a "Borrower"), jointly and severally promise to pay to the order of NATIONSBANK,
N.A., a national banking association, its successors and assigns (the "Lender"),
the principal sum of THREE MILLION DOLLARS  ($3,000,000)  (the "Principal Sum"),
or so much  thereof as has been or may be advanced or  readvanced  to or for the
account of the Borrowers  pursuant to the terms and  conditions of the Financing
Agreement (as hereinafter  defined),  together with interest thereon at the rate
or rates hereinafter provided, in accordance with the following:

     1. Interest.

          (a) Except as otherwise expressly set forth below, amounts outstanding
     hereunder shall bear interest at the LIBOR Rate (as  hereinafter  defined),
     plus two hundred and fifty basis points (i.e.  2.50%). For purposes hereof,
     the "LIBOR  Rate" shall mean a  fluctuating  rate equal to the daily London
     Interbank  Offered Rate for thirty (30) days U.S. Dollar deposits as quoted
     by the Lender as of 11:00 A.M. (Washington, D.C., time) (the "LIBOR Rate").
     The  interest  rate on all sums  accruing  interest at the LIBOR Rate under
     this Note shall change immediately and contemporaneously with any change in
     the LIBOR Rate.

          (b) In addition,  so long as no event of default or any act,  event or
     condition  which,  with  notice  or the  passage  of  time or  both,  would
     constitute an event of default  under any  Financing  Document has occurred
     and is  continuing,  the  Borrowers  shall  have the  right  to elect  that
     specified

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     amounts  advanced  under  this Note in a minimum  amount  of  $100,000  and
     increments  of  $50,000,  bear  interest  at the Prime Rate per annum.  For
     purposes  hereof,  the "Prime  Rate"  means the  fluctuating  prime rate of
     interest  established  and  declared by the Lender  from time to time.  The
     Prime  Rate does not  necessarily  represent  the lowest  rate of  interest
     charged by the Lender to its borrowers.

          (c) All  interest  payable  under  the  terms  of this  Note  shall be
     calculated  on the basis of a 360-day  year and the  actual  number of days
     elapsed.

          (d) In  respect  to any  interest  rate  election  hereunder  and  any
     transactions  contemplated  hereby,  the Borrowers  authorize the Lender to
     accept,  rely  upon,  act upon and  comply  with,  any  verbal  or  written
     instructions, requests, confirmations and orders of the President and Chief
     Executive  Officer,  the Vice President,  Treasure & Chief Financial Office
     and Vice President, Secretary & General Counsel on behalf of the Borrowers.
     The Borrowers  acknowledge that the transmission  between the Borrowers and
     the Lender of any such  instructions,  requests,  confirmations  and orders
     involves the possibility of errors,  omissions,  mistakes and discrepancies
     and agrees to adopt such internal  measures and  operational  procedures to
     protect its interests.  By reason thereof,  the Borrowers hereby assume all
     risk of loss and responsibility  for, release and discharge the Lender from
     any and all  responsibility  or  liability  for,  and  agree to  indemnify,
     reimburse on demand and hold the Lender  harmless from, any and all claims,
     actions,  damages, losses, liability and expenses by reason of, arising out
     of or in any way connected with or related to, (i) the Lender's acceptance,
     reliance  and actions  upon,  compliance  with or  observation  of any such
     instructions,  requests, confirmations or orders, and (ii) any such errors,
     omissions, mistakes and discrepancies,  except those caused by the Lender's
     gross negligence or willful misconduct.

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     2. Payments and Maturity.  The unpaid Principal Sum, together with interest
thereon at the rate or rates provided above, shall be payable as follows:

          (a) Interest only on the unpaid Principal Sum shall be due and payable
     monthly,  commencing  July 1,  1997,  and on the  same  day of  each  month
     thereafter to maturity; and

          (b) Unless  sooner  paid,  the unpaid  Principal  Sum,  together  with
     interest  accrued and unpaid  thereon,  shall be due and payable in full on
     November 30, 1998.

     The fact that the  balance  hereunder  may be  reduced to zero from time to
time pursuant to the Financing Agreement will not affect the continuing validity
of this Note or the Financing Agreement, and the balance may be increased to the
Principal Sum after any such reduction to zero.

     3.  Default  Interest.  Upon the  occurrence  of an Event  of  Default  (as
hereinafter defined), the unpaid Principal Sum shall bear interest thereafter at
a rate (the  "Default  Rate") two  percent  (2%) per annum in excess of the then
current  rate or rates of  interest  hereunder  until  such  Event of Default is
cured.

     4. Late Charges.  If the Borrowers shall fail to make any payment under the
terms of this Note within ten (10) days after the date such  payment is due, the
Borrowers  shall pay to the Lender on demand a late charge equal to five percent
(5%) of such payment.

     5. Application and Place of Payments. All payments, made on account of this
Note  shall  be  applied  first  to the  payment  of any  late  charge  then due
hereunder,  second to the  payment  of  accrued  and  unpaid  interest  then due
hereunder,  and the remainder,  if any, shall be applied to the unpaid Principal
Sum.  All  payments on account of this Note shall be paid in lawful money of the
United States of America in immediately  available funds during regular business
hours of the Lender at its principal office in McLean, Virginia or at such other
times and places as the Lender may at any

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time and from time to time designate in writing to the Borrowers.  The Lender is
authorized  to deduct  any  payment  (including  payments  of  principal  and/or
interest as above provided) from the Borrowers' Account Number  _____________ on
or after the date the payment is due; provided, however, that such authorization
shall not be deemed to relieve the Borrowers from their  obligation to make such
payment when it is due.

     6.  Prepayment.  The  Borrowers may prepay the Principal Sum in whole or in
part without premium or penalty.

     7.  Financing  Agreement and Other  Financing  Documents.  This Note is the
"Revolving  Promissory Note" described in a Financing and Security  Agreement of
even date  herewith  by and among the  Borrowers  and the  Lender  (as  amended,
modified, restated, substituted,  extended and renewed at any time and from time
to time, the "Financing Agreement").  The indebtedness evidenced by this Note is
included  within  the  meaning  of the  term  "Obligations"  as  defined  in the
Financing Agreement.  The term "Financing  Documents" as used in this Note, each
Acquisition Note, shall mean collectively this Note, the Financing Agreement and
any other instrument,  agreement,  or document  previously,  simultaneously,  or
hereafter  executed and  delivered  by the  Borrowers  and/or any other  person,
singularly or jointly with any other person, evidencing, securing, guaranteeing,
or in  connection  with the  Principal  Sum,  this  Note  and/or  the  Financing
Agreement.

     8. Security. This Note is secured as provided in the Financing Agreement.

     9. Events of Default.  The  occurrence  of any one or more of the following
events shall constitute an event of default (individually, an "Event of Default"
and collectively, the "Events of Default") under the terms of this Note:

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          (a) The failure of the  Borrowers to pay to the Lender within five (5)
     days of when due any and all amounts payable by the Borrowers to the Lender
     under the terms of this; or

          (b) The  occurrence of an event of default (as defined  therein) under
     the terms and conditions of any of the other Financing Documents.

     10. Remedies.  Upon the occurrence of an Event of Default, at the option of
the Lender,  all amounts  payable by the Borrowers to the Lender under the terms
of this Note shall  immediately  become due and  payable by the  Borrower to the
Lender without notice to the Borrowers or any other person, and the Lender shall
have all of the rights,  powers,  and remedies available under the terms of this
Note,  any of the  other  Financing  Documents  and  all  applicable  laws.  The
Borrowers and all endorsers, guarantors, and other parties who may now or in the
future be primarily or  secondarily  liable for the payment of the  indebtedness
evidenced by this Note hereby severally waive  presentment,  protest and demand,
notice of protest, notice of demand and of dishonor and non-payment of this Note
and expressly agree that this Note or any payment hereunder may be extended from
time to time without in any way affecting the joint and several liability of the
Borrowers, guarantors and endorsers.

     Until such time as the Lender is not committed to extend  further credit to
the  Borrowers  and all  Obligations  of the  Borrowers  to the Lender have been
indefeasibly  paid in full in cash,  and subject to and not in limitation of the
provisions set forth in the next following  paragraph  below,  no Borrower shall
have any right of subrogation (whether contractual, arising under the Bankruptcy
Code or otherwise),  reimbursement  or  contribution  from any Borrower,  or any
guarantor  nor any right of  recourse to its  security  for any of the debts and
obligations  of any  Borrower  which are the  subject  of this  Note.  Except as
otherwise  expressly permitted by the Financing  Agreement,  any and all present
and  future  debts and  obligations  of any  other to any  Borrower  are  hereby
subordinated to the

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full payment and  performance of all present and future debts and obligations to
the  Lender  under  this  Note and the  Financing  Agreement  and the  Financing
Documents, provided, however, notwithstanding anything set forth in this Note to
the contrary,  prior to the occurrence of a payment Default, the Borrowers shall
be permitted to make payments on account of any of such present and future debts
and obligations from time to time in accordance with the terms thereof.

     The Borrowers further agree that, if any payment made by the Borrowers,  or
any other person is applied to this Note and is at any time annulled, set aside,
rescinded,  invalidated,  declared to be fraudulent or preferential or otherwise
required to be refunded or repaid,  or the  proceeds of any  property  hereafter
securing  this Note is required  to be  returned by the Lender to any  Borrower,
their  estate,  trustee,  receiver  or  any  other  party,  including,   without
limitation,  such  Borrower,  under any  bankruptcy  law,  state or federal law,
common law or equitable cause, then, to the extent of such payment or repayment,
such Borrower's  liability  hereunder (and any lien,  security interest or other
collateral  securing  such  liability)  shall be and  remain  in full  force and
effect,  as fully as if such payment had never been made,  or, if prior  thereto
any such lien, security interest or other collateral hereafter securing such the
Borrower's  liability hereunder shall have been released or terminated by virtue
of such cancellation or surrender,  this Note (and such lien,  security interest
or other  collateral)  shall be  reinstated  in full force and effect,  and such
prior cancellation or surrender shall not diminish,  release,  discharge, impair
or  otherwise  affect the  obligations  of such  Borrower  of the amount of such
payment  (or any lien,  security  interest  or other  collateral  securing  such
obligation).

     The JOINT AND SEVERAL obligations of each Borrower under this Note shall be
absolute,  irrevocable  and  unconditional  and shall  remain in full  force and
effect  until the  outstanding  principal  of and  interest on this Note and all
other Obligations or amounts due hereunder and under the

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Financing  Agreement and the Financing  Documents  shall have been  indefeasibly
paid in full in cash in  accordance  with the terms  thereof and this Note shall
have been canceled.

     11.  Expenses.  The Borrowers  jointly and severally  promise to pay to the
Lender on demand by the Lender all costs and expenses  incurred by the Lender in
connection with the collection and enforcement of this Note, including,  without
limitation, reasonable attorneys' fees and expenses and all court costs.

     12. Notices. Any notice, request, or demand to or upon the Borrowers or the
Lender  shall be deemed to have been  properly  given or made when  delivered in
accordance with Section 11.01 of the Financing Agreement.

     13. Miscellaneous.  Each right, power, and remedy of the Lender as provided
for in this Note or any of the other  Financing  Documents,  or now or hereafter
existing  under  any  applicable  law  or  otherwise  shall  be  cumulative  and
concurrent  and shall be in  addition  to every other  right,  power,  or remedy
provided  for in this Note or any of the  other  Financing  Documents  or now or
hereafter  existing under any  applicable  law, and the exercise or beginning of
the  exercise  by the  Lender  of any one or more of  such  rights,  powers,  or
remedies shall not preclude the  simultaneous or later exercise by the Lender of
any or all such other rights,  powers,  or remedies.  No failure or delay by the
Lender to insist upon the strict performance of any term,  condition,  covenant,
or  agreement  of  this  Note or any of the  other  Financing  Documents,  or to
exercise any right,  power, or remedy  consequent  upon a breach thereof,  shall
constitute a waiver of any such term,  condition,  covenant,  or agreement or of
any such breach,  or preclude the Lender from exercising any such right,  power,
or remedy at a later time or times.  By accepting  payment after the due date of
any amount  payable under the terms of this Note, the Lender shall not be deemed
to waive the right either to require prompt payment when due

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of all other amounts payable under the terms of this Note or to declare an Event
of Default  for the  failure  to effect  such  prompt  payment of any such other
amount.  No course of dealing or conduct  shall be effective  to amend,  modify,
waive, release, or change any provisions of this Note.

     14.  Partial  Invalidity.  In the event any  provision of this Note (or any
part  of any  provision)  is held by a court  of  competent  jurisdiction  to be
invalid, illegal, or unenforceable in any respect, such invalidity,  illegality,
or  unenforceability  shall not affect any other provision (or remaining part of
the  affected  provision)  of this Note;  but this Note shall be construed as if
such invalid, illegal, or unenforceable provision (or part thereof) had not been
contained  in this  Note,  but only to the  extent it is  invalid,  illegal,  or
unenforceable.

     15.  Captions.  The captions herein set forth are for convenience  only and
shall not be deemed to define,  limit,  or describe  the scope or intent of this
Note.

     16.  Applicable Law. Each Borrower  acknowledges  and agrees that this Note
shall be governed by the laws of the  Commonwealth of Virginia,  even though for
the convenience  and at the request of the Borrowers,  this Note may be executed
elsewhere.

     17. WAIVER OF TRIAL BY JURY.  EACH BORROWER  HEREBY WAIVES TRIAL BY JURY IN
ANY ACTION OR PROCEEDING TO WHICH EITHER BORROWER AND THE LENDER MAY BE PARTIES,
ARISING OUT OF OR IN ANY WAY  PERTAINING  TO (A) THIS NOTE OR (B) THE  FINANCING
DOCUMENTS.  IT IS AGREED AND UNDERSTOOD THAT THIS WAIVER CONSTITUTES A WAIVER OF
TRIAL BY JURY OF ALL CLAIMS AGAINST ALL PARTIES TO SUCH ACTIONS OR  PROCEEDINGS,
INCLUDING CLAIMS AGAINST PARTIES WHO ARE NOT PARTIES TO THIS NOTE.

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     THIS WAIVER IS KNOWINGLY,  WILLINGLY AND VOLUNTARILY MADE BY EACH BORROWER,
AND EACH BORROWER HEREBY REPRESENTS THAT NO  REPRESENTATIONS  OF FACT OR OPINION
HAVE BEEN MADE BY ANY INDIVIDUAL TO INDUCE THIS WAIVER OF TRIAL BY JURY OR TO IN
ANY WAY MODIFY OR NULLIFY ITS EFFECT.  EACH BORROWER FURTHER  REPRESENTS THAT IT
HAS BEEN  REPRESENTED  IN THE  SIGNING  OF THIS  NOTE AND IN THE  MAKING OF THIS
WAIVER BY INDEPENDENT LEGAL COUNSEL,  SELECTED OF ITS OWN FREE WILL, AND THAT IT
HAS HAD THE OPPORTUNITY TO DISCUSS THIS WAIVER WITH COUNSEL.

     18.  ARBITRATION.  ANY  CONTROVERSY  OR CLAIM  BETWEEN OR AMONG THE PARTIES
HERETO  INCLUDING  BUT NOT  LIMITED  TO THOSE  ARISING  OUT OF THIS  NOTE OR ANY
RELATED  INSTRUMENTS,  AGREEMENTS OR DOCUMENTS,  INCLUDING ANY CLAIM BASED ON OR
ARISING FROM AN ALLEGED  TORT,  SHALL BE DETERMINED  BY BINDING  ARBITRATION  IN
ACCORDANCE  WITH  THE  FEDERAL  ARBITRATION  ACT  (OR  IF  NOT  APPLICABLE,  THE
APPLICABLE  STATE LAW),  THE RULES OF PRACTICE AND PROCEDURE FOR  ARBITRATION OF
COMMERCIAL DISPUTES OF ENDISPUTE,  INC., D/B/A  J.A.M.S./ENDISPUTE  ("J.A.M.S.")
AND THE "SPECIAL RULES" SET FORTH BELOW. IN THE EVENT OF AN  INCONSISTENCY,  THE
SPECIAL RULES SHALL CONTROL.  JUDGMENT UPON ANY ARBITRATION AWARD MAY BE ENTERED
IN ANY COURT HAVING  JURISDICTION.  ANY PARTY TO THIS  INSTRUMENT,  AGREEMENT OR
DOCUMENT MAY BRING ANY ACTION,  INCLUDING A SUMMARY OR EXPEDITED PROCEEDING,  TO
COMPEL ARBITRATION OF ANY

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CONTROVERSY OR CLAIM TO WHICH THIS NOTE RELATES IN ANY COURT HAVING JURISDICTION
OVER SUCH ACTION.

          (A) SPECIAL  RULES.  THE  ARBITRATION  SHALL BE  CONDUCTED  IN FAIRFAX
     COUNTY,   VIRGINIA  AND  ADMINISTERED  BY  J.A.M.S.  WHO  WILL  APPOINT  AN
     ARBITRATOR.  IF J.A.M.S.  IS UNABLE OR LEGALLY PRECLUDED FROM ADMINISTERING
     THE ARBITRATION,  THEN THE AMERICAN ARBITRATION ASSOCIATION WILL SERVE. ALL
     ARBITRATION  HEARINGS  WILL BE  COMMENCED  WITHIN  NINETY  (90) DAYS OF THE
     DEMAND FOR ARBITRATION;  FURTHER, THE ARBITRATOR SHALL ONLY, UPON A SHOWING
     OF CAUSE,  BE  PERMITTED  TO EXTEND THE  COMMENCING  OF SUCH HEARING FOR AN
     ADDITIONAL SIXTY (60) DAYS.

          (B)  RESERVATION  OF RIGHTS.  NOTHING IN THIS NOTE SHALL BE DEEMED TO:
     (I)  LIMIT  THE  APPLICABILITY  OF ANY  OTHERWISE  APPLICABLE  STATUTES  OF
     LIMITATION  OR  REPOSE  AND  ANY  WAIVERS  CONTAINED  IN  THIS  INSTRUMENT,
     AGREEMENT OR DOCUMENT;  OR (II) BE A WAIVER BY THE LENDER OF THE PROTECTION
     AFFORDED TO IT BY 12 U.S.C.  ss.91 OR ANY  SUBSTANTIALLY  EQUIVALENT  STATE
     LAW;  OR (III) LIMIT THE RIGHT OF THE  LENDER:  (A) TO  EXERCISE  SELF HELP
     REMEDIES SUCH AS (BUT NOT LIMITED TO) SET OFF, OR (B) TO FORECLOSE  AGAINST
     ANY REAL OR  PERSONAL  PROPERTY  COLLATERAL,  OR (C) TO OBTAIN FROM A COURT
     PROVISIONAL  OR ANCILLARY  REMEDIES SUCH AS (BUT NOT LIMITED TO) INJUNCTIVE
     RELIEF, WRIT OF POSSESSION OR THE APPOINTMENT OF A RECEIVER. THE LENDER MAY
     EXERCISE SUCH SELF HELP RIGHTS, FORECLOSE

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     UPON SUCH  PROPERTY,  OR OBTAIN  SUCH  PROVISIONAL  OR  ANCILLARY  REMEDIES
     BEFORE, DURING OR AFTER THE PENDENCY OF ANY ARBITRATION  PROCEEDING BROUGHT
     PURSUANT TO THIS INSTRUMENT, AGREEMENT OR DOCUMENT. NEITHER THE EXERCISE OF
     SELF HELP REMEDIES NOR THE  INSTITUTION  OR  MAINTENANCE  OF ANY ACTION FOR
     FORECLOSURE  OR FOR  PROVISIONAL OR ANCILLARY  REMEDIES SHALL  CONSTITUTE A
     WAIVER OF THE RIGHT OF ANY PARTY, INCLUDING THE CLAIMANT IN SUCH ACTION, TO
     ARBITRATE THE MERITS OF THE CONTROVERSY OR CLAIM OCCASIONING RESORT TO SUCH
     REMEDIES.

     IN WITNESS WHEREOF,  the Borrower has caused this Note to be executed under
seal by its duly authorized officers as of the date first written above.

WITNESS OR ATTEST:             VERSAR, INC.


/s/ Lula Fasold                By: /s/ Lawrence W. Sinnott            (SEAL)
--------------------------         --------------------------
                                   Name:  Lawrence W. Sinnott
                                   Title: V.P. and CFO

WITNESS OR ATTEST:             GEOMET TECHNOLOGIES, INC.


/s/ Lula Fasold                By: /s/ Lawrence W. Sinnott            (SEAL)
--------------------------         --------------------------
                                   Name:  Lawrence W. Sinnott
                                   Title: Treasurer


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