Salusbury, Thomas, Mathematical collections and translations (Tome I), 1667

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1then when they are in a ſtate of having a propenſion of moving
naturally to the ſame.
Tie a bottle that hath water in it, to
the end of a cord, and holding the other end faſt in your hand,
and making the cord and your arm the ſemi-diameter, and the
knitting of the ſhoulder the centre, ſwing the bottle very faſt
bout, ſo as that it may deſcribe the circumference of a circle,
which, whether it be parallel to the Horizon, or perpendicular to
it, or any way inclined, it ſhall in all caſes follow, that the
ter will not fall out of the bottle: nay, he that ſhall ſwing it,
ſhall find the cord always draw, and ſtrive to go farther from the
And if you bore a hole in the bottom of the bottle,
you ſhall ſee the water ſpout forth no leſs upwards into the skie,
than laterally, and downwards to the Earth; and if inſtead of
ter, you ſhall put little pebble ſtones into the bottle, and ſwing it
in the ſame manner, you ſhall find that they will ſtrive in the like
manner againſt the cord.
And laſtly, we ſee boys throw ſtones
a great way, by ſwinging round a piece of a ſtick, at the end of
which the ſtone is let into a ſlit (which ſtick is called by them a
ſling;) all which are arguments of the truth of the concluſion,
to wit, that the vertigo or ſwing conferreth upon the moveable,
a motion towards the circumference, in caſe the motion be ſwift:
and therefore if the Earth revolve about its own centre, the
tion of the ſuperficies, and eſpecially towards the great circle,
as being incomparably more ſwift than thoſe before named, ought
to extrude all things up into the air.
SIMP. The Argument ſeemeth to me very well proved and
inforced; and I believe it would be an hard matter to anſwer and
overthrow it.
SALV. Its ſolution dependeth upon certain notions no leſs
known and believed by you, than by my ſelf: but becauſe they
come not into your mind, therefore it is that you perceive not the
anſwer; wherefore, without telling you it (for that you know the
ſame already) I ſhall with onely aſſiſting your memory, make you
to refute this argument.
SIMP. I have often thought of your way of arguing, which
hath made me almoſt think that you lean to that opinion of Pla-

to, Quòd noſtrum ſcire ſit quoddam reminiſci; therefore I intreat
you to free me from this doubt, by letting me know your
Our krowledg is
a kind of
cence according to
SALV. What I think of the opinion of Plato, you may gather
from my words and actions.
I have already in the precedent
ferences expreſly declared my ſelf more than once; I will purſue
the ſame ſtyle in the preſent caſe, which may hereafter ſerve you
for an example, thereby the more eaſily to gather what my
nion is touching the attainment of knowledg, when a time ſhall

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