EXHIBIT 10.4
                               REVOLVING LOAN NOTE


$15,000,000                                                   October 22, 2002

      FOR VALUE  RECEIVED,  the  undersigned,  Tremont  Corporation,  a Delaware
corporation  ("Maker"),  promises  to pay, on or before  December  31, 2004 (the
"Maturity Date"), to the order of NL Industries,  Inc., a New Jersey corporation
("Payee") or any subsequent  holder,  at its offices at 16825 Northchase  Drive,
Suite  1200,  Houston TX 77060,  or such  other  place  designated  by holder in
writing,  the principal  sum of FIFTEEN  MILLION  ($15,000,000),  or such lesser
amount as shall equal the aggregate principal amount of all revolving loans made
to Maker by Payee hereunder (the "Revolving Loans"), together with interest from
the date hereof on the unpaid  balance of this Note as it may exist from time to
time at the rate (herein called the "Applicable Rate") of prime plus two percent
per annum, determined at the beginning of each calendar quarter, and in no event
shall the  Applicable  Rate exceed the maximum  interest  rate  permitted  to be
charged  from time to time under  applicable  law  (herein  called the  "Maximum
Rate").  Accrued interest on the unpaid principal of this Note shall be computed
on the basis of a 360-day  year  applied  to the  actual  number of days in each
calendar  month and shall be payable on the last  business day of each  calendar
quarter.  The Applicable Rate shall be determined based upon the published prime
rate.  Notwithstanding the foregoing, if at any time the Applicable Rate exceeds
the Maximum Rate, the rate of interest  payable under this Note shall be limited
to the Maximum Rate as provided above.

      Subject to the terms and  conditions  set forth in this Note,  Payee shall
make Revolving Loans to Maker at any time and from time to time from the date of
this Note until the  Maturity  Date,  in an  aggregate  principal  amount not to
exceed at any one time the Maximum  Revolving  Loan Amount (as defined below) at
such time. Revolving Loans made under this Note shall be in an integral multiple
of  $200,000  and shall be wired by Payee to the account of Maker  requested  by
Maker prior to 3:00 p.m.,  New York time, on the date  proposed by Maker.  Maker
shall give Payee irrevocable  written notice of all proposed Revolving Loans not
later than three  business  days prior to the proposed  borrowing (a  "Borrowing
Notice").  Such Borrowing Notice shall specify the aggregate principal amount of
the  Revolving  Loan that Maker is  requesting  Payee to make and the  requested
effective  date of the  proposed  Revolving  Loan,  and  shall  contain  Maker's
certification that no default exists, no default would,  solely with the passage
of time,  exist and that no  default  would  exist  after  giving  effect to the
requested  Revolving  Loan.  Each  Revolving  Loan  shall bear  interest  on the
outstanding  principal balance thereof from the date such Revolving Loan is made
at the Applicable  Rate. The "Maximum  Revolving Loan Amount" shall mean Fifteen
Million  Dollars  ($15,000,000),  subject to  reduction in  accordance  with the
provisions of this Note.

      Maker shall pay Payee on the last  business day of each  calendar  quarter
beginning  on December 31, 2002 and  simultaneously  with the payment in full of
this Note, in immediately  available funds, a revolving loan commitment fee (the
"Fee") equal to 1/2 of 1% per annum on the average unused amount of the Maximum


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      Revolving  Loan  Amount  during  such  quarter  (or,  if the Fee is  being
calculated  for a period  other than a quarter,  during such  period).  Such Fee
shall be computed on the basis of the actual  number of days elapsed over a year
of 360  days.  Such Fee  shall  commence  on the date of this  Note and cease to
accrue on the termination of Payee's commitment to make Revolving Loans.

      Maker shall have the right at any time,  in its sole  discretion  and upon
not less than 10 days written notice to Payee, to further  permanently reduce or
terminate  the Maximum  Revolving  Loan  Amount,  provided,  however,  that each
partial  reduction  thereof  shall be in an integral  multiple of $250,000.  Any
reduction of the Maximum  Revolving  Loan Amount shall be accompanied by payment
in full of any  principal  over the Maximum  Revolving  Loan Amount plus accrued
interest and accrued Fee computed as provided in the previous paragraph.

      The principal  balance of this Note may be prepaid and discharged in whole
or in part by Maker at any time and from time to time, without premium,  penalty
or fee.  Notwithstanding  the prior  sentence,  all interest that is accrued and
unpaid  with  respect to the  prepaid  principal  amount and the Fee accrued and
unpaid with respect to the unpaid Maximum Revolving Loan Amount shall be paid at
the time of the prepayment.

      The Maker,  signers,  sureties,  guarantors  and  endorsers  of this Note,
jointly and  severally,  except as otherwise  expressly set forth herein,  waive
demand, presentment,  notice of nonpayment or dishonor, diligence in collecting,
grace,  notice of any protest,  and consent to all extensions for any periods of
time and partial payments, before or after maturity.

      If this  Note is not paid at  maturity,  howsoever  such  maturity  may be
brought  about,  and  the  same  is  placed  in the  hands  of an  attorney  for
collection, or if this Note is collected by suit or through bankruptcy,  probate
or other legal  proceedings,  Maker agrees to pay holder's  costs of collection,
when incurred, including reasonable attorney's fees.

      No delay in the  payments  to  holder or in the  exercise  of any power or
right  under this  Note,  or under any  instrument  securing  payment  hereof or
executed in connection herewith,  shall operate as a waiver thereof, nor shall a
single or  partial  exercise  of any power or right  preclude  other or  further
exercise thereof or exercise of any other power or right.

      Payment  of the  indebtedness  evidenced  by this Note is  secured  by the
security  interests  established by a Security Agreement dated as of the date of
this Note executed by the Maker and Payee covering  certain  securities owned by
Maker (the "Security Documents").

      If at any  time  the  Payee  shall  notify  the  Maker  that a  Collateral
Deficiency (as hereinafter  defined) exits, then within 5 days of its receipt of
such notice, the Maker shall, at its option, do one of the following:

        (a) prepay principal amounts  outstanding under this Note, together with
            accrued and unpaid interest on such principal  amount to the date of
            prepayment,   so  that  immediately  following  such  prepayment  no
            Collateral Deficiency exists, or

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        (b) provide  the Payee with  additional  collateral  under the  Security
            Documents  reasonably  acceptable  to the Payee so that  immediately
            following  delivery  of such  additional  collateral  no  Collateral
            Deficiency exists.

      In the event a Collateral  Deficiency  occurs,  Payee's commitment to make
further Revolving Loans shall be terminated without notice, at the option of the
Payee, until such time as no Collateral Deficiency shall exist.

      For purposes of this Note, (a) a Collateral  Deficiency exists at any time
when the outstanding  principal amount together with accrued and unpaid interest
on the Note and the Fee  exceeds 20% of the  Collateral  Value,  (b)  Collateral
Value shall mean the Current  Market Value of all  securities  pledged under the
Security  Documents,  and (c)  Current  Market  Value shall mean the most recent
closing price of any security  pledged  under the Security  Documents on the New
York Stock Exchange or any other nationally  recognized  securities exchange, or
if such security is not listed on a national  securities  exchange,  the closing
price of such  security as reported on the National  Association  of  Securities
Dealers Automated Quotation System ("NASDAQ"), or, if applicable, the average of
the closing bid and ask quotation for such security as reported on the NASDAQ.

      The term default shall include any or all of the following:

            (a) The assignment,  voluntary or involuntary conveyance of legal or
      beneficial interest,  mortgage,  pledge or grant of a security interest in
      any of the Collateral (as defined in the Security Documents); or

            (b) The  filing or  issuance  of a notice of any lien,  warrant  for
      distraint or notice of levy for taxes or assessment against the Collateral
      (except  for those which are being  contested  in good faith and for which
      adequate reserves have been created); or

            (c) Maker's nonpayment of any installment of principal,  interest or
      the Fee under this Note; or

            (d) The  adjudication  of Maker as  bankrupt,  or the  taking of any
      voluntary action by Maker or any involuntary  action against Maker seeking
      an  adjudication  of Maker as  bankrupt,  or seeking  relief by or against
      Maker under any provision of the Bankruptcy  Code, or seeking  liquidation
      or dissolution of Maker;

            (e) Maker failing to comply with any other  covenant in this Note or
      in the Security Documents;

            (f)  Maker's  default  in any  payment  (regardless  of  amount)  of
      principal of or interest on any other indebtedness for borrowed money; or

            (g) Maker's  default in the  observance or  performance of any other
      agreement or condition relating to any such other indebtedness for


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      borrowed  money or contained  in any  instrument  evidencing,  securing or
      relating  thereto or any other event shall occur or condition  exist,  the
      effect of which  default or other event or  condition  is to cause,  or to
      permit the holder of the  indebtedness to cause,  such other  indebtedness
      for borrowed money to become due prior to its stated maturity.

      An "Event of Default"  shall be deemed to have occurred  immediately  upon
any default  described in clause (d) or (g) above,  if any default  described in
clauses  (c) or (f)  above  is not  cured  within  5  days,  and if any  default
described in clauses (a),  (b), or (e) is not cured within 30 days after written
notice from Payee to Maker.

      If an  Event  of  Default  has  occurred  and is  continuing,  the  entire
principal balance and accrued interest owing hereof shall at once become due and
payable and  Payee's  commitment  to make  Revolving  Loans shall be  terminated
without  notice,  at the option of the Payee,  and the  property  covered by the
Security  Documents shall be subject to foreclosure under the Security Documents
and  applicable  law.  Failure to exercise  this option  shall not  constitute a
waiver of the right to  exercise  the same  subsequently  or in the event of any
subsequent default. If any payment, including interest or principal, required to
be made under this Note is not made when due,  interest on the overdue sum shall
accrue at a rate of prime plus four percent.

      The  proceeds  of this Note shall be used (i) first,  to repay all amounts
owed by Maker to NL  Environmental  Management  Services,  Inc.  pursuant to the
Revolving Loan Note of Maker dated as of February 9, 2001, and (ii) second,  for
working capital or other purposes, as determined by Maker.

      So long as the Note shall remain  unpaid,  the Maker shall  furnish to the
Payee:

        (a) as soon as  available  and in any event not later than 45 days after
            the end of each of the first  three  quarters of each fiscal year of
            the Maker, the consolidated balance sheet of the Maker as of the end
            of such  quarter  and the  consolidated  statements  of  income  and
            retained  earnings  and  cash  flows  of the  Maker  for the  period
            commencing  at the end of the previous  year and ending with the end
            of such quarter,  all in reasonable  detail and duly  certified with
            respect  to  such  consolidated   statements  (subject  to  year-end
            adjustments)  by an officer of the Maker as having been  prepared in
            accordance with generally accepted accounting principles;

        (b) as soon as  available  and in any event not later than 90 days after
            the end of each fiscal year of the Maker, a copy of the annual audit
            report for such year for the Maker,  including therein  consolidated
            balance  sheets of the Maker as of the end of such  fiscal  year and
            consolidated  statements of income and retained earnings and of cash
            flows of the Maker for such fiscal year,  in each case  certified by
            PricewaterhouseCoopers  LLP or other  independent  certified  public
            accountants of recognized standing reasonably acceptable to Payee.

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      This Note shall be construed in accordance with the laws of the State of
New Jersey and the laws of the United States applicable to transactions in New
Jersey.

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      IN WITNESS WHEREOF, the undersigned Maker has executed this Note as of the
22 day of October, 2002.

                                       Tremont Corporation




                                       By: /s/ Mark A. Wallace
                                           -----------------------------------


                                       Its: Vice President
                                            ----------------------------------


Acknowledged and agreed to by the undersigned:

NL Industries, Inc.


By: /s/ Robert D. Hardy
    -----------------------------------


Its: Vice President
     ----------------------------------


















58135
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SCHEDULE OF REVOLVING LOANS

Type of Transaction
(Loan or Payment)                Date                  Amount
-------------------              ----                  ------



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