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

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1ſtence before the common centre of gravity: ſo that it is not one

centre alone, which is no other than indiviſible point, and therefore
of no efficacie, that can attract unto it grave matters; but that thoſe
matters conſpiring naturally to unite, form to themſelves a
mon centre, which is that about which parts of equal moment
conſiſt: ſo that I hold, that if the great aggregate of grave

dies were gathered all into any one place, the ſmall parts that were
ſeparated from their whole, would follow the ſame, and if they
were not hindered, would penetrate wherever they ſhould find
parts leſs grave than themſelves: but coming where they ſhould
meet with matters more grave, they would deſcend no farther.
And therefore I hold, that in the Cave full of air, the whole Vault
would preſs, and violently reſt it ſelf onely upon that air, in caſe
its hardneſs could not be overcome and broken by its gravity; but
looſe ſtones, I believe, would deſcend to the centre, and not ſwim
above in the air: nor may it be ſaid, that they move not to their
whole, though they move whither all the parts of the whole
would transfer themſelves, if all impediments were removed.
Things grave are
before the centre of
gravity.
The great maſs
of grave bodies
ing transferred out
of their place, the
ſeparated parts
maß.
SIMP. That which remaineth, is a certain Errour which he
ſerveth in a Diſciple of Copernicus, who making the Earth to
move with an annual motion, and a diurnal, in the ſame manner
as the Cart-wheel moveth upon the circle of the Earth, and in it
ſelf, did conſtitute the Terreſtrial Globe too great, or the great
Orb too little; for that 365 revolutions of the Æquinoctial, are
leſs by far than the circumference of the great Orb.
SALV. Take notice that you miſtake, and tell us the direct
contrary to what muſt needs be written in that Book; for you
ſhould ſay, that that ſame Copernican Author did conſtitute the
Terreſtrial Globe too little, and the great Orb too big; and not
the Terreſtrial Globe too big, and the annual too little.
SIMP. The miſtake is not mine; ſee here the words of the
Book. Non videt, quòd vel circulum annuum æquo minorem, vel
orbem terreum juſto multò fabricet majorem. (In Engliſh thus:)
He ſeeth not, that he either maketh the annual circle equal to the
leſs, or the Terreſtrial Orb much too big.
SALV. I cannot tell whether the firſt Author erred or no, ſince
the Author of this Tractate doth not name him; but the error of
this Book is certain and unpardonable, whether that follower of
Copernicus erred or not erred; for that your Author paſſeth by ſo
material an error, without either detecting or correcting it.
But
let him be forgiven this fault, as an error rather of inadvertencie,
than of any thing elſe: Farthermore, were it not, that I am
ready wearied and tired with talking and ſpending ſo mnch time
with very little profit, in theſe frivolous janglings and
tions, I could ſhew, that it is not impoſſible for a circle, though