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

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1and concrete: therefore let Simplicius plead in excuſe of this
Author; and whether he chinks that the Phyſicks can differ ſo
very much from the Mathematicks.
SIMP. The ſubſtractions are in my opinion inſufficient to ſalve
this difference, which is ſo extreamly too great to be reconciled:
and in this caſe I have no more to ſay but that, Quandoque bonus
dormitet Homerus. But ſuppoſing the calculation of ^{*} Salviatus

to be more exact, and that the time of the deſcent of the ball
were no more than three hours; yet me thinks, that coming from
the concave of the Moon, which is ſo great a diſtance off, it would
be an admirable thing, that it ſhould have an inſtinct of
ing it ſelf all the way over the ſelf-ſame point of the Earth, over
which it did hang in its departure thence and not rather be left a
very great way behind.
* Not
dus, as the Latine
ha hit.
SALV. The effect may be admirable, and not admirable, but
natural and ordinary, according as the things precedent may fall
For if the ball (according to the Authors ſuppoſitions)
whilſt it ſtaid in the concave of the Moon, had the circular motion
of twenty four hours together with the Earth, and with the reſt of
the things contained within the ſaid Concave; that very vertue
which made it turn round before its deſcent, will continue it in
the ſame motion in its deſcending.
And ſo far it is from not
ing pace with the motion of the Earth, and from ſtaying behind,
that it is more likely to out-go it; being that in its approaches to
the Earth, the motion of gyration is to be made with circles
tinually leſſer and leſſer; ſo that the ball retaining in it ſelf that
ſelf-ſame velocity which it had in the concave, it ought to
pate, as I have ſaid, the vertigo or converſion of the Earth. But
if the ball in the concave did want that circulation, it is not
ged in deſcending to maintain it ſelf perpendicularly over that
point of the Earth, which was juſt under it when the deſcent
Nor will Copernicus, or any of his followers affirm the
SIMP. But the Author maketh an objection, as you ſee,
manding on what principle this circular motion of grave and light
bodies, doth depend: that is, whether upon an internal or an
ternal principle.
SALV. Keeping to the Probleme of which we ſpeak, I ſay,
that that very principle which made the ball turn round, whil'ſt it
was in the Lunar concave, is the ſame that maintaineth alſo the
circulation in the deſcent: yet I leave the Author at liberty to
make it internal or external at his pleaſure.
SIMP. The Author proveth, that it can neither be inward nor
SALV. And I will ſay then, that the ball in the concave did

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