and conſequently ſome Years muſt be ſubſtracted from their Computation.
Astronomical Obſervations ſeem to have lent a ſtill greater Aſſiſtance to our Philoſopher. He appears to us ſtronger when he fights upon his own Ground.
You know that the Earth, beſides its annual Motion which carries it round the Sun from Weſt to Eaſt in the Space of a Year, has alſo a ſingular Revolution which was quite unknown till within theſe late Years. Its Poles have a very ſlow retrograde Motion from Eaſt to Weſt, whence it happens that their Poſition every Day does not correſpond exactly with the ſame Point of the Heavens. This Difference which is ſo inſenſible in a Year, becomes pretty conſiderable in Time; and in threeſcore and twelve Years the Difference is found to be of one Degree, that is to ſay, the three hundred and ſixtieth Part of the Circumference of the whole Heaven. Thus after ſeventy two Years the Colure of the vernal Equinox which paſs'd thro' a fix'd Star, correſponds with another fix'd Star. Hence it is, that the Sun,
inſtead
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