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                                                                      EXHIBIT 10


                     [Ferrofluidics Corporation Letterhead]


                                October 1, 1993


Mr. Alvan F. Chorney
32 Foxfire Drive
Sharon, MA 02067

Dear Mr. Chorney:

     This letter sets forth our understanding with respect to severance pay to
which you would be entitled in the event of termination of your employment under
certain circumstances.

     In the event that your employment with the Company is terminated by the
Company other than by reason of your death, disability or for cause, you will be
entitled to receive severance pay ("Severance Payment") for a period of eighteen
months at a rate equal to the higher of (i) $150,000 per annum or (ii) your
annual salary rate at the time of termination. The Severance Payment shall be
paid to you in 39 equal bi-weekly payments, commencing with the first pay date
of the Company following your termination of employment.

     For purposes of this Agreement, in the event you shall be totally disabled
from performing your duties with the Company for a consecutive period of
thirteen weeks, the Board of Directors may terminate your employment after one
(1) month prior written notice to you, in which event the Company shall not be
liable to pay you any further compensation or the severance payment.

     This Letter Agreement does not change in any way the at-will nature of your
employment with the Company, nor does it supersede the Non-Disclosure Agreement
dated January 29, 1990 between you and the Company which remains in full force
and effect.

     This Letter Agreement shall in all respects be interpreted, enforced,
governed and construed by and under the laws of the State of New Hampshire,
exclusive of the conflicts of laws provisions thereof.

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Mr. Alvan F. Chorney
October 1, 1993
Page Two




     This Letter Agreement represents our entire understanding regarding the
terms of your severance from the Company and supersedes any prior
understandings or agreements between you and the Company or any of its
representatives regarding the terms of your severance from the Company. This
Agreement may not be modified, altered or changed except by a written
instrument, altered or changed except by a written instrument duly signed by
the parties.

     Please signify your agreement to the terms of this Letter Agreement by
signing in the space provided.

                                   Sincerely,

                                   FERROFLUIDICS CORPORATION



                                   By:  /s/ Paul F. Avery, Jr.
                                       -------------------------------
                                        Paul F. Avery, Jr.
                                        Chief Executive Officer







Agreed to:



/s/ Alvan F. Chorney
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Alvan F. Chorney