EXHIBIT 10.15

                                 THIRD AMENDMENT
                   TO AMENDED AND RESTATED LOAN AGREEMENT


    THIS THIRD AMENDMENT TO AMENDED AND RESTATED LOAN AGREEMENT (the
"AMENDMENT"), dated as of April 30, 1998, is among SYNTRON, INC. (the
"COMPANY"), and WELLS FARGO BANK (TEXAS), NATIONAL ASSOCIATION (a "BANK"), and
WELLS FARGO BANK (TEXAS), NATIONAL ASSOCIATION, as agent for itself and the
other banks and lending institutions from time to time party thereto (the
"Agent").

                                R E C I T A L S:

    A.The Company, the Agent and the Bank entered into that certain Loan
Agreement, dated as of December 6, 1996, pursuant to which the Bank agreed to
make available to the Company revolving credit loans (as heretofore amended as
of April 30, 1997 and December 10, 1997 and as hereafter amended, modified or
supplemented from time to time, the "AGREEMENT").

    B.The Company, the Agent and the Bank now desire to amend the Agreement to
extend the Termination Date and as may otherwise herein be set forth.

    NOW, THEREFORE, in consideration of the premises herein contained and other
good and valuable considerations, the receipt and sufficiency of which are
hereby acknowledged, the parties hereto agree as follows intending to be legally
bound:

                                    ARTICLE I

                                   DEFINITIONS

    Section 1.1 DEFINITIONS. Capitalized terms used in this Amendment, to the
extent not otherwise defined herein, shall have the same meanings as in the
Agreement, as amended hereby.

                                   ARTICLE II

                                   AMENDMENTS

    Section 2.1 AMENDMENT TO ARTICLE 1. Effective as of the date hereof, each
reference to the date "April 30, 1998" contained in the definition of the term
"TERMINATION DATE" is hereby amended to read "October 30, 1998".

    Section 2.2 AMENDMENT TO SECTION 9.5. Section 9.5 is amended by adding the
following phrase at the end of the exception found therein: "and that during the
1998 fiscal year, the Borrower may make aggregate Capital Expenditures not to
exceed $12,000,000."
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                                   ARTICLE III

                              CONDITIONS PRECEDENT
    Section 3.1   CONDITIONS.   The   effectiveness   of  this  Amendment  is
subject to the satisfaction of the following conditions precedent:

      (a) The representations and warranties contained herein and in all other
Loan Documents, as amended hereby, shall be true and correct as of the date
hereof as if made on the date hereof.

      (b) No Event of Default shall have occurred and be continuing and no event
or condition shall have occurred that with the giving of notice or lapse of time
or both would be an Event of Default.

      (c) All corporate proceedings taken in connection with the transactions
contemplated by this Amendment and all documents, instruments, and other legal
matters incident thereto shall be satisfactory to the Agent and its legal
counsel.

                                   ARTICLE IV

                RATIFICATIONS, REPRESENTATIONS AND WARRANTIES
    Section 4.1   RATIFICATIONS.  The  terms  and  provisions  set  forth  in
this Amendment shall modify and supersede all inconsistent terms and provisions
set forth in the Agreement and the other Loan Documents and except as expressly
modified and superseded by this Amendment, the terms and provisions of the
Agreement and the other Loan Documents are ratified and confirmed and shall
continue in full force and effect. The Company, the Agent and the Bank agree
that the Agreement as amended hereby shall continue to be legal, valid, binding
and enforceable in accordance with its terms.

    Section 4.2 REPRESENTATIONS AND WARRANTIES. The Company hereby represents
and warrants to the Agent and the Bank that (i) the execution, delivery and
performance of this Amendment and any and all other Loan Documents executed or
delivered in connection herewith have been authorized by all requisite corporate
action on the part of the Company and will not violate the articles of
incorporation or bylaws of the Company, (ii) the representations and warranties
contained in the Agreement, as amended hereby, and any other Loan Document are
true and correct on and as of the date hereof as though made on and as of the
date hereof, (iii) no Event of Default has occurred and is continuing and no
event or condition has occurred that with the giving of notice or lapse of time
or both would be an Event of Default, and (iv) the Company is in full compliance
with all covenants and agreements contained in the Agreement as amended hereby.
                                    ARTICLE V

                                  MISCELLANEOUS
    Section 5.1 SURVIVAL OF REPRESENTATIONS AND WARRANTIES. All representations
and warranties made in this Amendment or any other Loan Document including any
Loan Document furnished in connection with this Amendment shall survive the
execution and delivery of this Amendment and the other Loan Documents, and no
investigation by the Agent or any Bank or any closing shall affect the
representations and warranties or the right of the Agent and each Bank to rely
upon them.

    Section 5.2 REFERENCE TO AGREEMENT. Each of the Loan Documents, including
the Agreement and any and all other agreements, documents, or instruments now or
hereafter executed and delivered pursuant to the terms hereof or pursuant to the
terms of the Agreement as amended hereby, are hereby amended so that any
reference in such Loan Documents to the Agreement shall mean a reference to the
Agreement as amended hereby.

    Section 5.3 EXPENSES OF THE AGENT. The Company agrees to pay on demand all
reasonable costs and expenses incurred by the Agent in connection with the
preparation, negotiation, and execution of this Amendment and the other Loan
Documents executed pursuant hereto and any and all amendments, modifications,
and supplements thereto, including without limitation the costs and fees of the
Agent's legal counsel, and all reasonable costs and expenses incurred by the
Agent in connection with the enforcement or preservation of any rights under the
Agreement, as amended hereby, or any other Loan Document, including without
limitation the costs and fees of the Agent's legal counsel.

    Section 5.4 SEVERABILITY. Any provision of this Amendment held by a court of
competent jurisdiction to be invalid or unenforceable shall not impair or
invalidate the remainder of this Amendment and the effect thereof shall be
confined to the provision so held to be invalid or unenforceable.

    Section 5.5 APPLICABLE LAW. THIS AMENDMENT AND ALL OTHER LOAN DOCUMENTS
EXECUTED PURSUANT HERETO SHALL BE DEEMED TO HAVE BEEN MADE AND TO BE PERFORMABLE
IN HOUSTON, HARRIS COUNTY, TEXAS AND SHALL BE GOVERNED BY AND CONSTRUED IN
ACCORDANCE WITH THE LAWS OF THE STATE OF TEXAS.

    Section 5.6 SUCCESSORS AND ASSIGNS. This Amendment is binding upon and shall
inure to the benefit of the Agent, the Bank and the Company and their respective
successors and assigns, except the Company may not assign or transfer any of its
rights or obligations hereunder without the prior written consent of the Agent
and each Bank.

    Section 5.7 COUNTERPARTS. This Amendment may be executed in one or more
counterparts, each of which when so executed shall be deemed to be an original,
but all of which when taken together shall constitute one and the same
instrument.

    Section 5.8 EFFECT OF WAIVER. No consent or waiver, express or implied, by
the Agent or any Bank to or for any breach of or deviation from any covenant,
condition or duty by the Company shall be deemed a consent or waiver to or of
any other breach of the same or any other covenant, condition or duty.
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    Section 5.9 HEADINGS. The headings, captions, and arrangements used in this
Amendment are for convenience only and shall not affect the interpretation of
this Amendment.

    Section 5.10 NON-APPLICATION OF CHAPTER 346 OF TEXAS FINANCE CODE. The
provisions of Chapter 346 of the Texas Finance Code (Vernon's Annotated Texas
Statutes) are specifically declared by the parties not to be applicable to this
Amendment or any of the Loan Documents or the transactions contemplated hereby.

    Section 5.11 ENTIRE AGREEMENT. THIS AMENDMENT, THE AGREEMENT AND THE OTHER
LOAN DOCUMENTS REPRESENT THE FINAL AGREEMENT AMONG THE PARTIES HERETO AND MAY
NOT BE CONTRADICTED BY EVIDENCE OF PRIOR, CONTEMPORANEOUS OR SUBSEQUENT ORAL
AGREEMENTS OF THE PARTIES HERETO. THERE ARE NO UNWRITTEN ORAL AGREEMENTS AMONG
THE PARTIES HERETO.

    Section 5.12  ARBITRATION.  This  Agreement  and the Loan  Documents  are
subject  to  the  arbitration   provisions  found  in  Sectin  12.16  of  the
Agreement.

      Executed as of the date first written above.

                                    COMPANY:

                                    SYNTRON, INC.


                                    By:   /s/ Ray F. Thompson
                                          Ray F. Thompson, Vice President


                                     AGENT:

                                    WELLS FARGO BANK (TEXAS), NATIONAL
                                    ASSOCIATION


                                    By:   /s/ David M. Anderson
                                          David M. Anderson, Vice President



                                      BANK:

                                    WELLS FARGO BANK (TEXAS), NATIONAL
                                    ASSOCIATION
<PAGE>
                                    By:   /s/ David M. Anderson
                                          David M. Anderson, Vice President

    The undersigned in its capacity as a guarantor hereby consents to the
execution of this Third Amendment to Loan Agreement pursuant to which the
Termination Date is extended and agrees that its guaranty issued pursuant to
that certain Limited Guaranty Agreement dated December 6, 1996 (the "Guaranty")
shall remain in full force and effect and continue to be the legal, valid and
binding obligation of the undersigned enforceable in accordance with its terms
to guaranty the Obligations as herein modified and extended. Notwithstanding
anything to the contrary contained in the Guaranty, the undersigned hereby
irrevocably waives any and all rights it may now or hereafter have under any
agreement, at law or in equity (including, without limitation, any law
subrogating the undersigned to the rights of Agent or any Bank) to assert any
claim against or seek contribution, indemnification or any other form of
reimbursement from the Company or any other party liable for payment of any or
all of the indebtedness guaranteed under the Guaranty for any payment made by
the undersigned under or in connection with the Guaranty or otherwise.

                                   GUARANTOR:

                                    TECH-SYM CORPORATION


                                    By:   /s/ Ray F. Thompson
                                          Ray F. Thompson, Vice President


                                    GEOSCIENCE CORPORATION


                                    By:   /s/ Ray F. Thompson
                                          Ray F. Thompson, Vice President