Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/175

 part but with two onely: but if the same bow be used, it always receiveth thence three degrees.

It doth so; and for this reason, shooting with the same bow in the chariots course, the shoots cannot be equal.

I had forgot to ask, with what velocity it is supposed in this particular experiment, that the chariot runneth.

The velocity of the chariot must be supposed to be one degree in comparison to that of the bow, which is three,

Very right, for so computation gives it. But tell me, when the chariot moveth, doth not all things in the same move with the same velocity?

Yes doubtless.

Then so doth the shaft also, and the bow, and the string, upon which the shaft is nock't.

They do so.

Why then, in discharging the shaft towards the course of the chariot, the bow impresseth its three degrees of velocity on a shaft that had one degree of velocity before, by means of the chariot which transported it so fast towards that part; so that in its going off it hath four degrees of velocity. On the contrary, in the other shoot, the same bow conferreth its same three degrees of velocity on a shaft that moveth the contrary way, with one degree; so that in its departing from the bow-string, it hath no more left but onely two degrees of velocity. But you your self have already said, that the way to make the shoots equal, is to cause that the shaft be let flie the first time with four degrees of velocity, and the second time with two. Therefore without changing the bow, the very course of the chariot is that which adjusteth the flights, and the experiment doth so represent them to any one who is not either wilfully or naturally incapable of reason. Now apply this discourse to Gunnery, and you shall find, that whether the Earth move or stand still, the shots made with the same force, will always curry equal ranges, to what part soever aimed. The error of Aristotle, Ptolomey, Tycho, your self, and all the rest, is grounded upon that fixed and strong persuasion, that the Earth standeth still, which you have not judgment nor power to depose, no not when you have a desire to argue of that which would ensue, presupposing the Earth to move. And thus, in the other argument, not considering that whil'st the stone is upon the Tower, it doth, as to moving or not moving, the same that the Terrestrial Globe doth, because you have concluded with your self, that the Earth stands still, you always discourse touching the fall of the stone, as if it were to depart from rest: whereas it behooveth to say, that if the Earth standeth still, the stone departeth from rest, and descendeth perpendicularly; but if the Earth do move, the stone