Galilei, Galileo Dialogues on two world systems 1661, tr. Salusbury, Thomas

author index 241 / 437      search

233
body that moveth, one of its extreams standing still without chan­
ching 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.

The Flexures in
animals are not
made for the di­
versity of motions.

The motions of
animals are of one
sort.

The ends of the
bones are all ro­
tund.

It is demonstra­
ted, that the ends
of the bones are of
necessity to be ro­
tund.

The motions of
animals are all
circular.

SIMP. 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.

Secondary moti­
ons of animals de­
pendent on the first

SALV. 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 ter­

restrial Globe is not required to move upon another part immove­
able, but that the motion is to be of the whole body, there is no
need in it of flexures.

The Terrestriall
Globe hath noe
need of flexures.

SIMP. This (will the aduersary rejoyn) might be, if the moti­
on were but one alone, but they being three, and those very dif­
ferent from each other, it is not possible that they should concur in

an ^{*} articulate body.

* Without joynts

SALV. 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 diffe­
rent 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 pro­
posed 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, Au­
thor 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 seem­
eth 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