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

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The conſtitution
of the Univerſe is
one of the moſt
ble Problems.
SAGR. I would not have you, Salviatus, meaſure our wits by
the ſcale of yours: you, who uſe to be continually buſied about
the ſublimeſt contemplations, eſteem thoſe notions frivolous and
below you, which we think matters worthy of our profoundeſt
thoughts: yet ſometimes for our ſatisfaction do not diſdain to
ſtoop ſo low as to give way a little to our curioſity.
As to the
refutation of the laſt argument, taken from the extruſions of the
diurnal vertigo, far leſs than what hath been ſaid, would have
given me ſatisfaction: and yet the things ſuperfluouſly ſpoken,
ſeemed to me ſo ingenious, that they have been ſo far from
rying my fancy, as that they have, by reaſon of their novelty,
tertained me all along with ſo great delight, that I know not how
to deſire greater: Therefore, if you have any other ſpeculation
to add, produce it, for I, as to my own particular, ſhall gladly
hearken to it.
SALV. I have always taken great delight in thoſe things which
I have had the fortune to diſcover, and next to that, which is my
chief content, I find great pleaſure in imparting them to ſome
friends, that apprehendeth and ſeemeth to like them: Now, in
gard you are one of theſe, ſlacking a little the reins of my
tion, which is much pleaſed when I ſhew my ſelf more
cacious, than ſome other that hath the reputation of a ſharp
ſight, I will for a full and true meaſure of the paſt diſpute,
duce another fallacy of the Sectators of Ptolomey and Ariſtotle,
which I take from the argument alledged.
SAGR. See how greedily I wait to hear it.
SALV. We have hitherto over-paſſed, and granted to Ptolomey,
as an effect indubitable, that the extruſion of the ſtone
ing from the velocity of the wheel turn'd round upon its centre,
the cauſe of the ſaid extruſion encreaſeth in proportion, as the
locity of the vertigo (or whirling) is augmented: from whence
it was inferred, that the velocity of the Earth's vertigo being
very much greater than that of any machin whatſoever, that we
can make to turn round artificially; the extruſion of ſtones, of
animals, &c.
would conſequently be far more violent. Now, I
obſerve that there is a great fallacy in this diſcourſe, in that we do
compare theſe velocities indifferently and abſolutely to one
It's true, that if I compare the velocities of the ſame wheel,
or of two wheels equal to each other, that which ſhall be more
ſwiftly turn'd round, ſhall extrude the ſtone with greater
lence; and the velocity encreaſing, the cauſe of the projection
ſhall likewiſe encreaſe: but when the velocity is augmented, not
by encreaſing the velocity in the ſame wheel, which would be by
cauſing it to make a greater number of revolutions in equal times;
but by encreaſing the diameter, and making the wheel greater, ſo
as that the converſion taking up the ſame time in the leſſer wheel,

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