EXHIBIT 10.8

                        FIRST AMENDMENT TO LOAN AGREEMENT

        THIS FIRST AMENDMENT TO LOAN AGREEMENT (the "Amendment"), dated as of
April 30, 1997, is between GEOSCIENCE CORPORATION (the "Company"), and WELLS
FARGO BANK (TEXAS), NATIONAL ASSOCIATION (the "Bank").

                                R E C I T A L S:

        A. The Company and the Bank entered into that certain Loan Agreement
(the "Agreement"), dated as of December 6, 1996, pursuant to which the Bank
agreed to make available to the Company revolving credit loans.

        B. The Company and the Bank now desire to amend the Agreement to extend
the Revolving Credit 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 AMENDMENTS TO SECTION 1.1. (a) Effective as of the date
hereof, each reference to the date "December 5, 1997" contained in the
definition of the term "REVOLVING CREDIT TERMINATION DATE" is hereby amended to
read "April 30, 1998."

               (b) Effective as of the date hereof, the term "CAPITAL
        EXPENDITURES" is amended in its entirety to read as follows:

                      "CAPITAL EXPENDITURES" means expenditures which, in
               accordance with GAAP, would be required to be capitalized on a
               consolidated balance sheet of the Borrower and its Subsidiaries;
               provided, however, that the term Capital Expenditures does not
               include "systems" manufactured, fabricated or assembled by the
               Borrower for sale or lease or other equipment held by the
               Borrower for sale or lease.
<PAGE>
        Section 2.2 AMENDMENT TO SECTION 9.5. Section 9.5 is amended by deleting
the number "6,000,000" and inserting in lieu thereof the number "12,000,000."

        Section 2.3 AMENDMENT TO EXHIBITS. Effective as of the date hereof,
EXHIBIT "A" to the Agreement is hereby amended to conform to ANNEX "I", attached
hereto.

                                   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 Bank shall have received the Revolving Credit Promissory
Note executed by the Company and dated as of a date satisfactory to the Bank.

               (b) 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.

               (c) 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.

               (d) 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 Bank 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 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 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

                                       -2-
<PAGE>
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 Bank or any closing shall affect the
representations and warranties or the right of the 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 BANK. The Company agrees to pay on demand
all reasonable costs and expenses incurred by the Bank 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
Bank's legal counsel, and all reasonable costs and expenses incurred by the Bank
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 Bank'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.

                                       -3-
<PAGE>
        Section 5.6 SUCCESSORS AND ASSIGNS. This Amendment is binding upon and
shall inure to the benefit of 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 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 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.

        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 15 OF TEXAS CREDIT CODE. The
provisions of Chapter 15 of the Texas Credit Code (Vernon's Annotated Texas
Statutes, Article 5069-15) 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 EMBODY THE FINAL, ENTIRE AGREEMENT AMONG THE PARTIES HERETO
RELATING TO THIS AMENDMENT AND SUPERSEDE ANY AND ALL PRIOR COMMITMENTS,
AGREEMENTS, REPRESENTATIONS AND UNDERSTANDINGS, WHETHER WRITTEN OR ORAL,
RELATING TO THIS AMENDMENT, AND MAY NOT BE CONTRADICTED OR VARIED BY EVIDENCE OF
PRIOR, CONTEMPORANEOUS OR SUBSEQUENT ORAL AGREEMENTS OR DISCUSSIONS OF THE
PARTIES HERETO. THERE ARE NO 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:

                                             GEOSCIENCE CORPORATION

                                             By:
                                                 Richard F. Miles, President

                                       -4-
<PAGE>
                                           Agent:

                                           WELLS FARGO BANK (TEXAS), NATIONAL

                                           ASSOCIATION

                                           By:
                                               David M. Anderson, Vice President

                                           Bank:

                                           WELLS FARGO BANK (TEXAS), NATIONAL
                                           ASSOCIATION

                                           By:
                                               David M. Anderson, Vice President

                                       -5-
<PAGE>
        The undersigned in its capacity as a guarantor hereby consents to the
execution of this Amendment to Loan Agreement 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 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:
                                            Wendell W. Gamel
                                            Chairman of the Board and President


                                       -6-
<PAGE>
                                    ANNEX "I"

                        REVOLVING CREDIT PROMISSORY NOTE

$3,000,000.00                   Houston, Texas                    April 30, 1997


    FOR VALUE RECEIVED, the undersigned, GEOSCIENCE CORPORATION, a Nevada
corporation ("Maker"), hereby promises to pay to the order of WELLS FARGO BANK
(TEXAS), NATIONAL ASSOCIATION, a national banking association ("Payee"), at its
offices at 1000 Louisiana, Houston, Harris County, Texas, in lawful money of the
United States of America, the principal sum of THREE MILLION AND NO/100 DOLLARS
($3,000,000.00), or so much thereof as may be advanced and outstanding
hereunder, together with interest on the outstanding principal balance from day
to day remaining, at a varying rate per annum which shall from day to day be
equal to the lesser of (a) the Maximum Rate (hereinafter defined) or (b) the
Selected Rate [as defined in the Agreement]); PROVIDED, HOWEVER, if at any time
the rate of interest specified in clause (b) preceding shall exceed the Maximum
Rate, thereby causing the interest rate hereon to be limited to the Maximum
Rate, then any subsequent reduction in the Selected Rate shall not reduce the
rate of interest hereon below the Maximum Rate until the total amount of
interest accrued hereon equals the amount of interest which would have accrued
hereon if the rate specified in clause (b) preceding had at all times been in
effect. Accrued and unpaid interest computed on the outstanding principal
balance hereof from day to day outstanding shall be due and payable on (i) the
last day of each respective Interest Period with respect to such respective
Eurodollar Borrowing (as such terms are defined in the Agreement) and (ii) on
the first day of each calendar month with respect to Floating Rate Borrowings
(as such term is defined in the Agreement). All principal of and accrued and
unpaid interest on this Note shall be due and payable on the Revolving Credit
Termination Date (as defined in the Agreement), and at any earlier maturity
(regardless of how such maturity is brought about, whether by acceleration or
otherwise). All past due principal and interest shall bear interest at the
Default Rate (hereinafter defined).

    As used in this Note, the following terms shall have the respective meanings
indicated below:

               "AGREEMENT" means that certain Loan Agreement dated December 6,
    1996, as the same was, from time to time, amended, between Maker and Payee,
    as amended the same has been amended by that certain First Amendement to
    Loan Agreement, dated of even date herewith, as the same may be amended,
    restated, modified, supplemented or otherwise changed from time to time.

               "DEFAULT RATE" means the Maximum Rate of, if no Maximum Rate
    exists, the sum of the Prime Rate in effect from day to day plus five
    percent.

                                     Page 1 of 5 Pages
<PAGE>
               "MAXIMUM RATE" means the maximum rate of nonusurious interest
    permitted from day to day by applicable law, including as to Article
    5069-1.04, Vernon's Texas Civil Statutes (and as the same may be
    incorporated by reference in other Texas statutes), but otherwise without
    limitation, that rate based upon the "indicated rate ceiling" and calculated
    after taking into account any and all relevant fees, payments, and other
    charges in respect of this Note which are deemed to be interest under
    applicable law.

               "PRIME RATE" means that variable rate of interest per annum
    established by Payee from time to time as its "prime rate." Such rate is set
    by Payee as a general reference rate of interest, taking into account such
    factors as Payee may deem appropriate, it being understood that many of
    Payee's commercial or other loans are priced in relation to such rate, that
    it is not necessarily the lowest or best rate charged to any customer and
    that Payee may make various commercial or other loans at rates of interest
    having no relationship to such rate.

    This Note is the Note provided for in the Agreement. Maker may prepay the
principal of this Note upon the terms and conditions specified in the Agreement.
Maker may borrow, repay, and reborrow hereunder upon the terms and conditions
specified in the Agreement.

    Notwithstanding anything to the contrary contained herein, no provisions of
this Note shall require the payment or permit the collection of interest in
excess of the Maximum Rate. If any excess of interest in such respect is herein
provided for, or shall be adjudicated to be so provided, in this Note or
otherwise in connection with this loan transaction, the provisions of this
paragraph shall govern and prevail, and neither Maker nor the sureties,
guarantors, successors or assigns of Maker shall be obligated to pay the excess
amount of such interest, or any other excess sum paid for the use, forbearance,
or detention of sums loaned pursuant hereto. If for any reason interest in
excess of the Maximum Rate shall be deemed charged, required or permitted by any
court of competent jurisdiction, any such excess shall be applied as a payment
and reduction of the principal of indebtedness evidenced by this Note; and, if
the principal amount hereof has been paid in full, any remaining excess shall
forthwith be paid to Maker. In determining whether or not the interest paid or
payable exceeds the Maximum Rate. Maker and Payee shall, to the extent permitted
by applicable law, (i) characterize any non-principal payment as an expense,
fee, or premium rather than as interest, (ii) exclude voluntary prepayments and
the effects thereof, and (iii) amortize, prorate, allocate, and spread in equal
or unequal parts the total amount of interest throughout the entire contemplated
term of the indebtedness evidenced by this Note so that the interest for the
entire term does not exceed the Maximum Rate.

    If a default occurs in the payment of principal, interest or any other
amounts due under this Note, or upon the occurrence of any other Event of
Default, as such term is defined in the Agreement, the holder hereof may, at its
option, take any and all action available to the holder hereof to enforce
payment and performance of this Note, under this Note, the Agreement, the Loan
Documents, as such term is defined in the Agreement, at law, in equity or
otherwise. All such remedies shall be cumulative and not exclusive. Without
limiting the generality of the foregoing, the holder hereof may:

                                Page 2 of 5 Pages
<PAGE>
               (i) declare the entire unpaid principal balance of and accrued
        and unpaid interest on this Note immediately due and payable without
        notice, demand or presentment, all of which are hereby waived, and upon
        such declaration, the same shall become and shall be immediately due and
        payable; provided, however, that upon the occurrence of an Event of
        Default under Sections 9.01(d) or (e) of the Agreement, the entire
        unpaid principal balance of and accrued and unpaid interest on this Note
        shall become immediately due and payable without notice, demand or
        presentment, all of which are without notice, demand or presentment, all
        of which are hereby waived, and upon such declaration, the same shall
        become and shall be immediately due and payable;

              (ii) foreclose or otherwise enforce all liens or security interest
        securing payment hereof, or any part hereof;

             (iii) pursue Maker, any guarantor, surety endorser or other party
        ever liable for any amounts due and owing under this Note by whatever
        legal means are available to the holder hereof; and

              (iv) setoff against this Note any amounts owed by the holder
        hereof to Maker.

        If the holder hereof expends any effort in any attempt to enforce
payment of all or any part of installment of any sum due the holder hereunder,
or if this Note is placed in the hands of an attorney for collection, or if it
is collected through any legal proceedings, Maker agrees to pay all costs,
expenses, and fees incurred by the holder, including all reasonable attorneys'
fees.

        THIS NOTE SHALL BE GOVERNED BY AND CONSTRUED IN ACCORDANCE WITH THE LAWS
OF THE STATE OF TEXAS AND THE APPLICABLE LAWS OF THE UNITED STATES OF AMERICA.
THIS NOTE IS PERFORMABLE IN HARRIS COUNTY, TEXAS. ANY ACTION OR PROCEEDING UNDER
OR IN CONNECTION WITH THIS NOTE AGAINST MAKER OR ANY OTHER PARTY EVER LIABLE FOR
PAYMENT OF ANY SUMS OF MONEY PAYABLE ON THIS NOTE MAY BE BROUGHT IN ANY STATE OR
FEDERAL COURT IN HARRIS COUNTY, TEXAS. MAKER AND EACH SUCH OTHER PARTY HEREBY
IRREVOCABLY (I) SUBMITS TO THE NONEXCLUSIVE JURISDICTION OF SUCH COURTS, AND
(II) WAIVES ANY OBJECTION IT MAY NOW OR HEREAFTER HAVE AS TO THE VENUE OF ANY
SUCH ACTION OR PROCEEDING BROUGHT IN SUCH COURT OR THAT SUCH COURT IS AN
INCONVENIENT FORUM. NOTHING HEREIN SHALL AFFECT THE RIGHT OF PAYEE TO BRING ANY
ACTION OR PROCEEDING AGAINST MAKER OR ANY OTHER PARTY LIABLE HEREUNDER OR WITH
RESPECT TO ANY COLLATERAL IN ANY STATE OR FEDERAL COURT IN ANY OTHER
JURISDICTION. ANY ACTION OR PROCEEDING BY MAKER OR ANY OTHER PARTY LIABLE
HEREUNDER AGAINST PAYEE SHALL BE BROUGHT ONLY IN A COURT LOCATED IN HARRIS
COUNTY, TEXAS.

                                Page 3 of 5 Pages
<PAGE>
        Maker and each surety, guarantor, endorser, and other party ever liable
for payment of any sums of money payable on this Note jointly and severally
waive notice, presentment, demand for payment, protest, notice of protest and
non-payment or dishonor, notice of acceleration, notice of intent to accelerate,
notice of intent to demand, diligence in collecting, grace, and all other
formalities of any kind, and consent to all extensions without notice for any
period or periods of time and partial payments, before or after maturity, and
any impairment of any collateral securing this Note, all without prejudice to
the holder. The holder shall similarly have the right to deal in any way, at any
time, with one or more of the foregoing parties without notice to any other
party, and to grant any such party any extensions of time for payment of any of
said indebtedness, or to release or substitute part or all of the collateral
securing this Note, or to grant any other indulgences or forebearances
whatsoever, without notice to any other party and without in any way affecting
the personal liability of any party hereunder.

        This Note is executed in renewal, extension, modification and
rearrangement of, but not in discharge of, that certain promissory note dated
December 6, 1996, executed by the Maker and payable to the order of the Payee in
the original principal amount of $3,000,000.

                                            GEOSCIENCE CORPORATION

                                            By:
                                               Richard F. Miles, President


                                Page 4 of 5 Pages