Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/157

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132
G. Galilæus, his Systeme.

Salv.And was you so credulous,Many experiments, and reasons against the cause of the motion of projects, assigned by Aristotle. as to suffer your self to be perswaded to believe these fopperies, so long as you had your senses about you to confute them, and to understand the truth thereof? Therefore tell me, that great stone, and that Canon bullet, which but onely laid upon a table, did continue immoveable against the most impetuous winds, according as you a little before did affirm, if it had been a ball of cork or other light stuffe, think you that the wind would have removed it from its place?

Simpl.Yes, and I am assured that it would have blown it quite away, and with so much more velocity, by how much the matter was lighter, for upon this reason we see the clouds to be transported with a velocity equal to that of the wind that drives them.

Salv.And what is the Wind?

Simpl.The Wind is defined to be nothing else but air moved.

Salv.Then the moved air doth carry light things more swiftly, and to a greater distance, then it doth heavy.

Simpl.Yes certainly.

Salv.But if you were to throw with your arm a stone, and a lock of cotton wool, which would move swiftest and farthest?

Simpl.The stone by much; nay the wool would fall at my feet.

Salv.But, if that which moveth the projected substance, after it is delivered from the hand, be no other than the air moved by the arm, and the moved air do more easily bear away light than grave matters, how cometh it that the project of wool flieth not farther, and swifter than that of stone? Certainly it argueth that the stone hath some other impulse besides the motion of the air. Furthermore, if two strings of equal length did hang at yonder beam, and at the end of one there was fastened a bullet of lead, and a ball of cotton wool at the other, and both were carried to an equal distance from the perpendicular, and then let go; it is not to be doubted, but that both the one and the other would move towards the perpendicular, and that being carried by their own impetus, they would go a certain space beyond it, and afterwards return thither again. But which of these two pendent Globes do you think, would continue longest in motion, before that it would come to rest in its perpendicularity?

Simpl.The ball of lead would swing to and again many times, and that of wool but two or three at the most.

Salv.So that the impetus and that mobility whatsoever is the cause thereof, would conserve its self longer in grave substances, than light; I proceed now to another particular, and demand of you, why the air doth not carry away that Lemon which is upon that same Table?

Simp.