Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/172

 circle C I, the circumference shall be double to the circumference, and every arch of the greater circle double to every like arch of the lesser; and consequently, the half of the arch of the greater circle, equal to the whole arch of the lesse. And because the angle C E I made in the centre E of the lesser circle, and which insisteth upon the arch CI, is double the angle C A D, made in the centre A of the greater circle, to which the arch C D subtendeth; therefore the arch C D is half of the arch of the greater circle like to the arch C I, and therefore the two arches C D and C I are equal; and in the same manner we may demonstrate of all their parts. But that the business, as to the motion of descending grave bodies, proceedeth exactly thus, I will not at this time affirm; but this I will say, that if the line described by the cadent moveable be not exactly the same with this, it doth extream neerly resemble the same.

But I,Salviatus, am just now considering another particular very admirable; and this it is; That admitting these considerations, the right motion doth go wholly * mounting, and that Nature never makes use thereof, since that, even that that use, which was from the beginning granted to it, which was of reducing the parts of integral bodies to their place, when they were separated from their whole, and therefore constituted in a depraved disposition, is taken from it, and assigned to the circular motion.

This would necessarily follow, if it were concluded that the Terrestrial Globe moveth circularly; a thing, which I pretend not to be done, but have onely hitherto attempted, as I shall still, to examine the strength of those reasons, which have been alledged by Philosophers to prove the immobility of the Earth, of which this first taken from things falling perpendicularly, hath begat the doubts, that have been mentioned; which I know not of what force they may have seemed to Simplicius; and therefore before I passe to the examination of the remaining arguments, it would be convenient that he produce what he hath to reply to the contrary.

As to this first, I confesse indeed that I have heard sundry pretty notions, which I never thought upon before, and in regard they are new unto me, I cannot have answers so ready for them, but this argument taken from things falling perpendicularly, I esteem it not one of the strongest proofs of the mobility of the Earth; and I know not what may happen touching the shots of great Guns, especially those aimed contrary to the diurnal motion.

The flying of the birds as much puzzleth me as the objection of the Gun-shot, and all the other experiments above