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                                                               Exhibit 3(a)

                            CERTIFICATE OF AMENDMENT
                            ------------------------

                                       OF
                                       --

                     RESTATED CERTIFICATE OF INCORPORATION
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       CABOT CORPORATION, a corporation organized and existing under
and by virtue of the General Corporation Law of the State of
Delaware,

DOES HEREBY CERTIFY:

      FIRST: That the Board of Directors of said Corporation, by
unanimous written consent and agreement in lieu of a formal meeting,
dated as of November 21, 1984, adopted a vote setting forth the
proposed amendment to the Restated Certificate of Incorporation of
said Corporation, declaring said amendment to be advisable and
recommending the adoption of said amendment by vote of the
stockholders of the Corporation at its Annual Meeting of
Stockholders called for February 8, 1985. The vote setting forth
the proposed amendment is as follows:

VOTED: That the Restated Certificate of Incorporation of this Corporation
be amended, subject to stockholder approval, as follows:

1. by renumbering the present Articles "TENTH" and "ELEVENTH" as
   "ELEVENTH" and "TWELFTH".

2. by adding the following language at the end of newly numbered Article
   ELEVENTH:

       "Notwithstanding any provision of law, this restated
       certificate of incorporation or the by-laws of this corporation
       (and notwithstanding the fact that a lesser percentage may be
       specified by law, this restated certificate of incorporation or
       the by-laws of this corporation), and in addition to any
       affirmative vote of the holders of any class of preferred stock of
       this corporation outstanding or any other class of capital stock
       of this corporation or any series of any of the foregoing then
       outstanding which is required by law or by or pursuant to this

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      restated certificate of incorporation, the affirmative vote of the
      holders of 66-2/3 percent or more of the voting power of the
      shares of the then outstanding shares of stock of all classes and
      series of this corporation entitled to vote generally in the
      election of directors, voting together as a single class, shall be
      required to alter, amend or repeal paragraph (a), (b) or (c) of
      Article EIGHTH or Article TENTH of this restated certificate of
      incorporation or to adopt any provision inconsistent therewith."

3. by adding a new Article TENTH as follows:

      "TENTH: 1. Vote Required for Certain Business Combinations.

          In addition to any affirmative vote required by law or this
   restated certificate of incorporation, and except as otherwise
   expressly provided in section 2 of this Article TENTH:

             (a) Any merger or consolidation of this corporation or any
      subsidiary (as hereinafter defined) with (1) any interested
      stockholder (as hereinafter defined) or (2) any other corporation
      or other person (whether or not itself an interested stockholder)
      which is, or after such merger or consolidation would be, an
      affiliate (as hereinafter defined) of an interested stockholder; or

             (b) Any plan of exchange for all outstanding shares of this
      corporation or any subsidiary or for any class of shares of either
      with (1) any interested stockholder or (2) any other corporation
      or other person (whether or not itself an interested stockholder)
      which is, or after such plan of exchange would be, an affiliate of
      an interested stockholder; or

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          (c) Any sale, lease, exchange, mortgage, pledge, transfer or
   other disposition (in one transaction or a series of transactions)
   to or with any interested stockholder or any affiliate of any
   interested stockholder of any assets of this corporation or any
   subsidiary having an aggregate fair market value (as hereinafter
   defined) of $20,000,000 or more; or

          (d) The issuance or transfer by this corporation or any
   subsidiary (in one transaction or a series of transactions) of any
   securities of this corporation or any subsidiary to any interested
   stockholder or any affiliate of any interested stockholder in
   exchange for cash, securities or other property (or a combination
   thereof) having an aggregate fair market value of $20,000,000 or
   more; or

          (e) The adoption of any plan or proposal for the liquidation
   or dissolution of this corporation proposed by or on behalf of an
   interested stockholder or any affiliate of any interested
   stockholder; or

          (f) Any reclassification of securities (including any reverse
   stock split), or recapitalization of this corporation, or any
   merger or consolidation of this corporation with any of its
   subsidiaries or any other transaction (whether or not with or into
   or otherwise involving an interested stockholder) which has the
   effect, directly or indirectly, of increasing the proportionate
   share of the outstanding shares of any class of stock or
   securities convertible into stock of this corporation or any
   subsidiary which is directly or indirectly owned by any interested
   stockholder or any affiliate of any interested stockholder;

shall require the affirmative vote of the holders of at least 66 2/3
percent of the combined voting power of the then outstanding shares of

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 stock of all classes and series of this corporation entitled to vote
 generally in the election of directors (the "voting stock"), in each
 case voting together as a single class. Such affirmative vote shall
 be required notwithstanding the fact that no vote may be required, or
 that a lesser percentage may be specified, by law or by this restated
 certificate of incorporation or any vote or votes adopted pursuant to
 Article THIRD of this restated certificate of incorporation or in any
 agreement with any national securities exchange or otherwise.

        2. When Higher Vote is not Required. The provisions of this
 Article TENTH shall not be applicable to any particular business
 combination (as hereinafter defined), and such business combination
 shall require only such affirmative vote as is required by law, any
 other provision of this restated certificate of incorporation, any
 preferred stock designation or any agreement with any national
 securities exchange, if, all of the conditions specified in either of
 the following paragraphs (a) and (b) are met:

        (a) Approval by Continuing Directors. The business combination
 shall have been approved by a majority of the continuing directors (as
hereinafter defined), it being understood that this condition shall
not be capable of satisfaction unless there is at least one continuing
director; or

        (b) Price and Procedure Requirements. All of the following
 conditions shall have been met:

           (1) The aggregate amount of the cash and the fair market
    value as of the date of the consummation of the business
    combination of any consideration other than cash to be received
    per share by holders of common stock (as hereinafter defined) in
    such business combination shall be at least equal to the highest
    of the following:

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   (A) (if applicable) the highest per share price (including
   any brokerage commissions, transfer taxes and soliciting
   dealers' fees) paid by the interested stockholder for any
   shares of common stock acquired by it (i) within the two-year
   period immediately prior to the first public announcement of
   the proposal of the business combination (the "announcement
   date") or (ii) in the transaction in which it became an
   interested stockholder, whichever is higher; or

   (B) the fair market value per share of common stock on the
   announcement date or on the date on which the interested
   stockholder became an interested stockholder (such latter date
   is referred to in this Article TENTH as the "determination
   date"), whichever is higher; or

   (C) (if applicable) the price per share equal to the fair
   market value per share of common stock determined pursuant to
   paragraph (b)(1)(B) above, multiplied by the ratio of (i) the
   highest per share price (including any brokerage commissions,
   transfer taxes and soliciting dealers' fees) paid by the
   interested stockholder for any shares of common stock acquired
   by it within the two-year period immediately prior to the
   announcement date to (ii) the fair market value per share of
   common stock on the first day in such two-year period upon
   which the interested stockholder acquired any shares of common
   stock; and

       (2) The consideration to be received by holders of a
particular class or series of outstanding voting stock (including
common stock) shall be in cash or in the same form as the
interested stockholder has previously paid for shares of such
class. If the interested stockholder has paid for shares of
voting stock with varying forms of consideration, the form of

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consideration to be received by holders of such class or series of
voting stock shall be either cash or the form used to acquire
beneficially the largest number of shares of such class or series
of voting stock previously acquired by it; and

       (3) After such interested stockholder has become an
interested stockholder and prior to the consummation of such
business combination:

              (A) except as approved by a majority of the continuing
directors, there shall have been no failure to declare and pay at
the regular date therefor any full quarterly dividends (whether or
not cumulative) on any outstanding preferred stock;

              (B) there shall have been (i) no reduction in the annual
rate of dividends paid on the common stock (except as necessary to
reflect any subdivision of the common stock), except as approved
by a majority of the continuing directors, and (ii) an increase in
such annual rate of dividends as necessary to reflect any
reclassification (including any reverse stock split),
recapitalization, reorganization or any similar transaction which
has the effect of reducing the number of outstanding shares of the
common stock, unless the failure so to increase such annual rate
is approved by a majority of the continuing directors; and

              (C) such interested stockholder shall not have become the
beneficial owner of any additional shares of voting stock except
as part of the transaction in which it became an interested
stockholder; and

       (4) After such interested stockholder has become an
interested stockholder, such interested stockholder shall not have
received the benefit, directly or indirectly (except
proportionately as a stockholder), of any loans, advances,

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guarantees, pledges or other financial assistance or any tax
credits or other tax advantages provided by the corporation,
whether in anticipation of or in connection with such business
combination or otherwise; and

       (5) A proxy or information statement describing the proposed
business combination and complying with the requirements of the
Securities Exchange Act of 1934 (the "1934 Act") and the rules and
regulations thereunder (or any subsequent provisions replacing
such 1934 Act, rules or regulations) shall be mailed to public
stockholders of the corporation at least 30 days prior to the
consummation of such business combination (whether or not such
proxy or information statement is required to be mailed pursuant
to the 1934 Act or subsequent provisions).

3. Certain Definitions. For the purposes of this Article TENTH:

       (a) "affiliate" or "associate" has the respective meanings
ascribed to such terms in Rule 12b-2 of the General Rules and
Regulations under the 1934 Act, as in effect on February 8, 1985.

       (b) "board" means the board of directors of this corporation.

       (c) A person is a "beneficial owner" of any voting stock:

         (1) which such person or any of its affiliates or
       associates beneficially owns, directly or indirectly; or

         (2) which such person or any of its affiliates or
       associates has (A) the right to acquire (whether such right is
       exercisable immediately or only after the passage of time),
       pursuant to any agreement, arrangement or understanding or
       upon the exercise of conversion rights, exchange rights,
       warrants or options, or otherwise, or (B) the right to vote or
       direct the vote pursuant to any agreement, arrangement or
       understanding; or

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        (3) which are beneficially owned, directly or indirectly,
   by any other person with which such person or any of its
   affiliates or associates has any agreement, arrangement or
   understanding for the purpose of acquiring, holding, voting or
   disposing of any shares of voting stock.

       (d) The term "business combination" means any transaction
which is referred to in any one or more of paragraphs (a) through
(f) of Section 1.

       (e) "common stock" means the common capital stock of this
corporation.

       (f) "continuing director" means any member of the board who
is unaffiliated with and not a nominee of the interested
stockholder and was a member of the board prior to the time that
the interested stockholder became an interested stockholder, and
any successor of a continuing director who is unaffiliated with,
and not a nominee of the interested stockholder and who is
recommended to succeed a continuing director by a majority of
continuing directors then on the board.

        (g) "fair market value" means: (1) in the case of stock, the
 highest closing sale price during the 30-day period immediately
 preceding the date in question of a share of such stock on the
 Composite Tape for New York Stock Exchange-Listed Stocks, or, if
 such stock is not quoted on the Composite Tape, on the New York
 Stock Exchange, or, if such stock is not listed on such Exchange,
 on the principal United States securities exchange registered
 under the 1934 Act on which such stock is listed, or, if such
 stock is not listed on any such exchange, the highest closing
 price or bid quotation with respect to a share of such stock
 during the 30-day period preceding the date in question on the

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National Association of Securities Dealers, Inc. Automated
Quotations System or any system then in use, or if no such
quotations are available, the fair market value on the date in
question of a share of such stock as determined by a majority of
the continuing directors in good faith; and (2) in the case of
stock that is not traded on any United States registered
securities exchange nor in any over-the-counter market or in the
case of property other than cash or stock, the fair market value
of such property on the date in question as determined by a
majority of the continuing directors in good faith.

       (h) "interested stockholder" means any person (other than
this corporation or any subsidiary) who or which:

          (1) is the beneficial owner, directly or indirectly, of
   more than 10 percent of the combined voting power of the then
   outstanding voting stock; or

          (2) is an affiliate of the corporation and at any time
   within the two-year period immediately prior to the date in
   question was the beneficial owner, directly or indirectly, of
   10 percent or more of the voting power of the then outstanding
   voting stock; or

          (3) is an assignee of or has otherwise succeeded to the
   beneficial ownership of any shares of voting stock which were
   at any time within the two-year period immediately prior to
   the date in question beneficially owned by any interested
   stockholder, if such assignment or succession shall have
   occurred in the course of a transaction or series of
   transactions not involving a public offering within the
   meaning of the Securities Act of 1933.

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          For the purpose of determining whether a person is an
   interested stockholder pursuant to this paragraph (h) of this
   Section 3, the number of shares of voting stock deemed to be
   outstanding shall include shares deemed owned through application
   of paragraph (c) of this section 3 but shall not include any other
   shares of voting stock which may be issuable pursuant to any
   agreement, arrangement or understanding, or upon exercise of
   conversion rights, warrants or options, or otherwise.

          (i) A "person" means any individual, firm, corporation, group
   (as such term is used in Rule 13d of the General Rules and
   Regulations under the 1934 Act as in effect on February 8, 1985)
   or other entity.

          (j) "subsidiary" means any corporation of which a majority of
   any class of equity security is owned, directly or indirectly, by
   this corporation; provided, however, that for the purposes of the
   definition of interested stockholder set forth in paragraph (h) of
   this section 3, the term "subsidiary" means only a corporation of
   which a majority of each class of equity security is owned,
   directly or indirectly, by this corporation.

       4. Powers of the Board. A majority of the continuing directors
shall have the power and duty to determine for the purposes of this
Article TENTH, on the basis of information known to them after
reasonable inquiry, all facts necessary to determine compliance with
this Article TENTH, including without limitation, (a) whether a person
is an interested stockholder; (b) the number of shares of voting stock
beneficially owned by any person; (c) whether a person is an affiliate
or associate of another person; (d) whether the requirements of
section 2.(b) of this Article TENTH have been met with respect to any
proposed business combination, and (e) whether the assets which are
the subject of any business combination have, or the consideration to

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   be received for the issuance or transfer of securities by this
   corporation or any subsidiary in any business combination has, an
   aggregate fair market value of $20,000,000 or more. Any such
   determination made in good faith shall be binding and conclusive for
   all purposes of this Article TENTH.

          5. No Effect on Fiduciary Obligations of Interested
   Stockholders. Nothing contained in this Article TENTH shall be
   construed to relieve any interested stockholder from any fiduciary
   obligation imposed by law."

       SECOND: That thereafter, pursuant to vote of its Board of Directors,
the Annual Meeting of Stockholders of said Corporation was duly called
and held, upon notice in accordance with Section 222 of the General
Corporation Law of the State of Delaware, at which meeting the necessary
number of shares as required by statute were voted in favor of the
amendment.

       THIRD: That said amendments were duly adopted in accordance with the
applicable provision of Section 242 of the General Corporation Law of the
State of Delaware.

      FOURTH: That the capital of said Corporation shall not be reduced
under or by reason of said amendment.

       IN WITNESS WHEREOF, said CABOT CORPORATION has caused this
certificate to be signed by Robert A. Charpie, its President, and
attested by Henley R. Webb, its Assistant Secretary this 11th day of
February, 1985.

ATTEST:                                CABOT CORPORATION
                                      
/s/ Henley R. Webb                     By /s/ Robert A. Charpie
- ----------------------                    ----------------------
Assistant Secretary                       President