SECOND AMENDMENT OF SUBORDINATION AGREEMENT

     THIS SECOND AMENDMENT OF SUBORDINATION AGREEMENT (this "Amendment"), dated
as of December 22, 1998, is between SLOUGH ESTATES USA INC. ("Slough Estates"),
f/k/a SLOUGH PARKS INCORPORATED ("Slough Parks"), and U.S. BANK NATIONAL
ASSOCIATION ("USB"), f/k/a COLORADO NATIONAL BANK ("CNB").

                                       RECITALS

     A.   Slough Parks and CNB executed and delivered a Subordination Agreement
dated as of December 20, 1996 (the "Subordination Agreement"), pursuant to
which, among other things, Slough Parks subordinated certain obligations owed to
Slough Parks by Tipperary Corporation, a Texas corporation ("Borrower"), to any
and all obligations owed to CNB by Borrower under or in connection with a
Revolving Credit and Term Loan Agreement dated as of March 30, 1992, as amended
(the "Loan Agreement"), among Borrower, et al. and CNB.  The Subordination
Agreement was afterwards amended by an Amendment to Subordination Agreement and
Consent of Subordinating Party, dated as of February 13, 1998, between Slough
Parks and USB.

     B.   USB is the successor to CNB.  Slough Estates is the same entity as
Slough Parks.

     C.   Slough Estates and Borrower are executing a Promissory Note, dated
December 22, 1998, in the principal amount of $5.5 million (the "Replacement
Subordinated Note"), which shall constitute all or a part of the "Subordinated
Obligations" as defined in the Subordination Agreement.  In connection with the
Replacement Subordinated Note, the "Subordinated Note," as defined in the
Subordination Agreement, will be paid and the related "Pledged Interest," as
defined in the Subordination Agreement," will be released.  Repayment of the
Replacement Subordinated Note, pursuant to a Security Agreement of even date
therewith (the "Security Agreement"), is secured in part by a security interest
in all material, consolidated  assets of Debtor located in the United States
(excluding (1) any and all properties and assets covered or purported to be
covered by the Third Amended and Restated Mortgage, Deed of Trust, Assignment of
Proceeds, Security Agreement and Financing Statement (Oil and Gas) dated March
30, 1992, effective as of October 4, 1990, from Debtor, et al., for the benefit
of U.S. Bank National Association f/k/a Colorado National Bank f/k/a Central
Bank National Association ("Senior Lender"), (2) any and all properties and
assets covered or purported to be covered by the Negative Pledge Agreement dated
as of March 31, 1994 from Debtor, et al., for the benefit of Senior Lender, (3)
any and all other oil and/or gas properties and related assets to which Senior
Lender has given value in determining the "Borrowing Base" pursuant to the Loan
Agreement, and (4) any and all proceeds of the property and assets described in
(1) through (3) above), subject to certain otherwise permitted liens as set
forth in the Security Agreement (such collateral securing the Replacement
Subordinated Note, the "Replacement Pledged Interest").

     D.   The execution and delivery of this Amendment by Slough Estates is
required in order for the Replacement Subordinated Note and Security Agreement
to be in conformity with the Loan Agreement.

                                      AMENDMENT

     NOW THEREFORE, in consideration of $10.00 and other good and valuable
consideration, the receipt and sufficiency of which are hereby acknowledged:

     1.   All references in the Subordination Agreement to "Slough Parks
Incorporated" or "Subordinating Party" shall be deemed to be references to
Slough Estates USA Inc. f/k/a Slough Parks

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Incorporated.

     2.   As of, and after the execution of this Amendment, all references in
the Subordination Agreement (i) to the Subordinated Note shall be deemed to be
to the Replacement Subordinated Note, as herein defined, and (ii) to the Pledged
Interest shall be deemed to be to the Replacement Pledged Interest, as herein
defined. 

     3.   This Amendment may be executed in any number of counterparts, each of
which shall be an original and no one of which need be signed by all of the
parties, but all of which together shall constitute one and the same instrument.

     4.   Slough Estates hereby ratifies the Subordination Agreement and
confirms that it remains valid, enforceable and in full force and effect, as
amended.

SLOUGH ESTATES USA INC.                 U.S. BANK NATIONAL ASSOCIATION
 f/k/a SLOUGH PARKS INCORPORATED         f/k/a COLORADO NATIONAL BANK


By:                                     By:
   ---------------------------------       ------------------------------------
   Randall W. Rohner, Vice President       Charles S. Searle, Senior Vice
   And Chief Financial Officer             President


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