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

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1Tower. And this is the cauſe why the right motion made along
the ſide of the Tower appeareth to us more and more accelerate.
It appeareth alſo, how by reaſon of the infinite acuteneſſe of
the contact of thoſe two circles D C, C I, the receſſion of the
cadent moveable from the circumference C F D; namely, from
the top of the Tower, is towards the beginning extream ſmall,
which is as much as if one ſaid its motion downwards is very ſlow,
and more and more ſlow in infinitum, according to its vicinity to
the term C, that is to the ſtate of reſt.
And laſtly it is ſeen how
in the end this ſame motion goeth to terminate in the centre of the
Earth A.
The line
bed by a moveable
in its natural
ſcent, the motion
of the Earth
bout its own centre
being preſuppoſed,
would probably be
the circumference
of a circle.
SAGR. I underſtand all this very well, nor can I perſwade my
ſelf that the falling moveable doth deſcribe with the centre of its
gravity any other line, but ſuch an one as this.
SALV. But ſtay a little Sagredus, for I am to acquaint you
alſo with three Obſervations of mine, that its poſſible will not

pleaſe you.
The firſt of which is, that if we do well conſider, the
moveable moveth not really with any more than onely one motion
ſimply circular, as when being placed upon the Tower, it moved
with one ſingle and circular motion.
The ſecond is yet more

ſant; for, it moveth neither more nor leſſe then if it had ſtaid
tinually upon the Tower, being that to the arches C F, F G, G H,
that it would have paſſed continuing alwayes upon the Tower,
the arches of the circumference C I are exactly equal, anſwering
under the ſame C F, F G, G H, &c.
Whence followeth the third

wonder, That the true and real motion of the ſtone is never
lerated, but alwayes even and uniforme, ſince that all the equal
ches noted in the circumference C D, and their reſpondent ones
marked in the circumference C I, are paſt in equal times; ſo that
we are left at liberty to ſeek new cauſes of acceleration, or of
ther motions, ſeeing that the moveable, as well ſtanding upon the
Tower, as deſcending thence, alwayes moveth in the ſame faſhion,
that is, circularly, with the ſame velocity, and with the ſame
Now tell me what you think of this my fantaſtical
A moveable
ting from the top of
the Tower, moveth
in the
rence of a circle.
It moveth neither
more nor leſſe, than
if it had ſtaid
wayes there.
It moveth with
an uniform, not
an accelerate
SAGR. I muſt tell you, that I cannot with words ſufficiently
expreſſe how admirable it ſeemeth to me; and for what at
ſent offereth it ſelf to my underſtanding, I cannot think that the
buſineſs happeneth otherwiſe; and would to God that all the
demonſtrations of Philoſophers were but half ſo probable as this.
However for my perfect ſatisfaction I would gladly hear how you
prove thoſe arches to be equal.
SALV. The demonſtration is moſt eaſie. Suppoſe to your ſelf
a line drawn from I to E.
And the Semidiameter of the circle CD,
that is, the line C A, being double the Semidiameter C E of the

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