Exhibit 10.4

                               FIRST AMENDMENT TO
                       PLAN AND AGREEMENT OF DISTRIBUTION


        This first amendment TO THE Plan and Agreement of Distribution (this
"Amendment") is made as of the 27th day of December, 2001 by and between Thermo
Electron Corporation, a Delaware corporation ("Thermo Electron"), and Kadant
Inc., a Delaware corporation ("Kadant"). Capitalized terms used herein without
definition shall have the same meanings ascribed to such terms in the
Distribution Agreement (as defined below).

                                    RECITALS

        WHEREAS, Thermo Electron and Kadant are parties to that certain Plan and
Agreement of Distribution dated as of August 3, 2001 (the "Distribution
Agreement");

        WHEREAS, the parties hereto desire to amend the Distribution Agreement
as herein provided:

        NOW THEREFORE, in consideration of the covenants and agreements
contained herein and for other good and valuable consideration, the receipt and
sufficiency of which is hereby acknowledged, the parties hereto hereby agree as
follows:

        1.     That Section 9.6(a) of the Distribution Agreement is amended and
restated in its entirety to read as follows:

        9.6    Financial Covenants.

               (a)    Kadant will not, for so long as the guarantee by Thermo
Electron of obligations under the Kadant Debentures is outstanding:

               (i)    permit Net Debt divided by Net Capital to be greater than
                      40% measured at the end of each fiscal quarter commencing
                      on September 29, 2001; or

               (ii)   permit the quotient obtained by dividing (x) the sum of
                      EBITA and Interest Income by (y) Interest Expense to be
                      less than 4.0, measured at the end of each fiscal quarter
                      commencing on September 29, 2001 on an annualized basis
                      using the quarter then ended and the previous three
                      quarters.

               Notwithstanding the foregoing, in the event that the percentage
calculated in paragraph (i) of this Section 9.6 is less than or equal to 20% for
any measurement date, the required quotient specified in paragraph (ii) of this
Section 9.6 shall be lowered from 4.0 to 3.0 (measured at the end of each fiscal
quarter on an annualized basis using the quarter then ended and the previous
three quarters) for such period.





        2.     This Amendment and the rights and obligations of the parties
hereunder shall be construed in accordance with and governed by the laws of the
State of Delaware.

        3.     This Amendment may be executed in counterparts, each of which
shall be considered an original, but all of which together shall constitute one
and the same agreement.

        4.     At all times on and after the date hereof, all references in the
Distribution Agreement and each of the Ancillary Agreements to the Distribution
Agreement shall be deemed to be references to such Distribution Agreement after
giving effect to this Amendment.


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        IN WITNESS WHEREOF, the parties hereto have executed this Amendment as
of the date first set forth above.



                                   THERMO ELECTRON CORPORATION



                                   By:  /s/Kenneth J. Apicerno
                                        ----------------------------------------
                                        Name:   Kenneth J. Apicerno
                                        Title:  Treasurer



                                   KADANT INC.



                                   By:  /s/Thomas M. O'Brien
                                        ----------------------------------------
                                        Name:   Thomas M. O'Brien
                                        Title:  Executive Vice President and CFO