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

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1circle C I, the circumference ſhall be double to the circumference,
and every arch of the greater circle double to every like arch of
the leſſer; and conſequently, the half of the arch of the greater
circle, equal to the whole arch of the leſſe.
And becauſe the
gle C E I made in the centre E of the leſſer circle, and which
ſteth upon the arch C I, is double the angle C A D, made in the
centre A of the greater circle, to which the arch C D ſubtendeth;
therefore the arch C D is half of the arch of the greater circle like
to the arch C I, and therefore the two arches C D and C I are
qual; and in the ſame manner we may demonſtrate of all their
But that the buſineſs, as to the motion of deſcending grave
bodies, proceedeth exactly thus, I will not at this time affirm; but
this I will ſay, that if the line deſcribed by the cadent moveable
be not exactly the ſame with this, it doth extream neerly reſemble
the ſame.
SAGR. But I, Salviatus, am juſt now conſidering another

ticular very admirable; and this it is; That admitting theſe
ſiderations, the right motion doth go wholly ^{*} mounting, and that

Nature never makes uſe thereof, ſince that, even that that uſe,
which was from the beginning granted to it, which was of
cing the parts of integral bodies to their place, when they were
ſeparated from their whole, and therefore conſtituted in a
ved diſpoſition, is taken from it, and aſſigned to the circular
Right motion
ſeemeth wholly
cluded in nature.
* Vadia del tutto a
monte, rendered in
the Latixe
no peſſum eat.
SALV. This would neceſſarily follow, if it were concluded
that the Terreſtrial Globe moveth circularly; a thing, which I
pretend not to be done, but have onely hitherto attempted, as I
ſhall ſtill, to examine the ſtrength of thoſe reaſons, which have
been alledged by Philoſophers to prove the immobility of the
Earth, of which this firſt taken from things falling
larly, hath begat the doubts, that have been mentioned; which
I know not of what force they may have ſeemed to Simplicius;
and therefore before I paſſe to the examination of the remaining
arguments, it would be convenient that he produce what he hath
to reply to the contrary.
SIMP. As to this firſt, I confeſſe indeed that I have heard
ſundry pretty notions, which I never thought upon before, and
in regard they are new unto me, I cannot have anſwers ſo ready
for them, but this argument taken from things falling
cularly, I eſteem it not one of the ſtrongeſt proofs of the
lity of the Earth; and I know not what may happen touching the
ſhots of great Guns, eſpecially thoſe aimed contrary to the
nal motion.
SAGR. The flying of the birds as much puzzleth me as the
objection of the Gun-ſhot, and all the other experiments above

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