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Rh paper; but they rest more on a metaphysical than a scientific basis, and are to-day justly forgotten.

In 1782 writes, in regard to some of his discoveries of double stars:

"These may serve another very important end. I will just mention it, though it is foreign to my present purpose. Several stars of the first magnitude have been observed or suspected to have a proper motion; hence we may surmise that our sun, with all its planets and comets, may also have a motion towards some particular point of the heavens.... If this surmise should have any foundation, it will show itself in a series of some years in a kind of systematical parallax, or change, due to the motion of the whole solar system."

In 1783 he published his paper On the Proper Motion of the Solar System, which contained the proofs of his surmises of a year before. That certain of the stars had in fact a proper motion had been well established by the astronomers of the eighteenth century.