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December 27 1812: Jefferson on Perpetual Motion Machines




After an absence of five weeks at a distant possession of mine, to which I pay such visits three or four times a year, I find here your favor of November 30th.  I am very thankful to you for the description of Redhefer’s machine.  I had never before been able to form an idea of what his principle of deception was.  He is the first of the inventors of perpetual motion within my knowledge, who has had the cunning to put his visitors on a false pursuit, by amusing them with a sham machinery whose loose and vibratory motion might impose on them the belief that it is the real source of the motion they see.  To this device he is indebted for a more extensive delusion than I have before witnessed on this point.  We are full of it as far as this State, and I know not how much farther.  In Richmond they have done me the honor to quote me as having said that it was a possible thing.  A poor Frenchman who called on me the other day, with another invention of perpetual motion, assured me that Dr. Franklin, many years ago, expressed his opinion to him that it was not impossible.  Without entering into contest on this abuse of the Doctor’s name, I gave him the answer I had given to others before, that the Almighty himself could not construct a machine of perpetual motion while the laws exist which He has prescribed for the government of matter in our system ;  that the equilibrium established by Him between cause and effect must be suspended to effect that purpose.  But Redhefer seems to be reaping a rich harvest from the public deception.  The office of science is to instruct the ignorant.  Would it be unworthy of some one of its votaries who witness this deception, to give a popular demonstration of the insufficiency of the ostensible machinery, and of course of the necessary existence of some hidden mover?  And who could do it with more effect on the public mind than yourself ? I received, at the same time, the Abbe Rochon’s pamphlets and book on his application of the double refraction of the Iceland Spath to the measure of small angles.  I was intimate with him in France, and had received there, in many conversations, explanations of what is contained in these sheets.  I possess, too, one of his lunettes which he had given to Dr. Franklin, and which came to me through Mr. Hopkinson.  You are therefore probably acquainted with it.  The graduated bar on each side is 12 inches long.  The one extending to 37' of angle, the other to 3,438 diameter in distance of the object viewed.  On so large a scale of graduation, a nonias might distinctly enough subdivide the divisions of 10" to 10" each ;  which is certainly a great degree of precision.  But not possessing the common micrometer of two semi-lenses, I am not able to judge of their comparative merit. 

        —Thomas Jefferson, Monticello, writes to Dr. Robert Patterson, December 27, 1812

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