Page:Mathematical collections and translations, in two tomes - Salusbury (1661).djvu/258

 body that moveth, one of its extreams standing still without chanching place, the motion must needs be circular, and no other: and because in the living creatures moving, one of its members doth not separate from the other its conterminal, therefore that motion is of necessity circular.

How can this be? For I see the animal move with an hundred motions that are not circular, and very different from one another, as to run, to skip, to climbe, to descend, to swim, and many others.

Tis well: but these are secondary motions, depending on the preceding motions of the joynts and flexures. Upon the plying of the legs to the knees, and the thighs to the hips, which are circular motions of the parts, is produced, as consequents, the skip, or running, which are motions of the whole body, and these may possibly not be circular. Now because one part of the terrestrial Globe is not required to move upon another part immoveable, but that the motion is to be of the whole body, there is no need in it of flexures.

This (will the aduersary rejoyn) might be, if the motion were but one alone, but they being three, and those very different from each other, it is not possible that they should concur in an * articulate body.

I verily believe that this would be the answer of the Philosopher. Against which I make opposition another way; and ask you, whether you think that by way of joynts and flexures one may adapt the terrestrial Globe to the participation of three different circular motions? Do you not answer me? Seeing you are speechlesse, I will undertake to answer for the Philosopher, who would absolutely reply that they might; for that otherwise it would have been superfluous, and besides the purpose to have proposed to consideration, that nature maketh the flexions, to the end, the moveable may move with different motions; and that therefore the terrestrial Globe having no flexures, it cannot have those three motions which are ascribed to it. For if he had thought, that neither by help of flexures, it could be rendered apt for such motions, he would have freely affirmed, that the Globe could not move with three motions. Now granting this, I intreat you, and by you, if it were possible, that Philosopher, Author of the Argument, to be so courteous as to teach me in what manner those flexures should be accommodated, so that those three motions might commodiously be excercised; and I grant you four or six moneths time to think of an answer. As to me, it seemeth that one principle onely may cause a plurality of motions in the Terrestrial Globe, just in the same manner that, as I told you before, one onely principle with the help of various instruments