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

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1from the piece; and the departing from the ſtate of reſt, cannot
be, unleſſe the immobility of the Terreſtrial Globe be
ſed, which is the concluſion of that was in diſpute; Therefore,
I reply, that thoſe who make the Earth moveable, anſwer, that
the piece, and the ball that is in it, partake of the ſame motion
with the Earth; nay that they have this together with her from
nature; and that therefore the ball departs in no other manner
from its quieſcence, but conjoyned with its motion about the
tre, the which by its projection upwards, is neither taken away,
nor hindered; and in this manner following, the univerſal motion
of the Earth towards the Eaſt, it alwayes keepeth perpendicular
over the ſaid piece, as well in its riſe as in its return.
And the
ſame you ſee to enſue, in making the experiment in a ſhip with
a bullet ſhot upwards perpendicularly with a Croſſe-bow, which
returneth to the ſame place whether the ſhip doth move, or ſtand

An inſtance
gainst the diurnal
motion of the earth,
taken from the ſhot
of a Peece of
The anſwer to the
objection, ſhewing
the equivoke.
Another anſwer
to the ſame
SAGR. This ſatisfieth very well to all; but becauſe that I have
ſeen that Simplicius taketh pleaſure with certain ſubtilties to
puzzle his companions, I will demand of him whether,
ſing for this time that the Earth ſtandeth ſtill, and the piece
cted upon it perpendicularly, directed to our Zenith, he do at all
queſtion that to be the true perpendicular ſhot, and that the ball
in departing, and in its return is to go by the ſame right line,
ſtill ſuppoſing all external and accidental impediments to be
SIMP. I underſtand that the matter ought to ſucceed exactly
in that manner.
SAGR. But if the piece were placed, not perpendicularly, but
inclining towards ſome place, what would the motion of the ball
Would it go haply, as in the other ſhot, by the
cular line, and return again by the ſame?
SIMP. It would not ſo do; but iſſuing out of the piece, it
would purſue its motion by a right line which prolongeth the
rect perpendicularity of the concave cylinder of the piece, unleſſe
ſo far as its own weight would make it decline from that erection
towards the Earth.
SAGR. So that the mounture of the cylinder is the regulator of
the motion of the ball, nor doth it, or would it move out of that
line, if its own gravity did not make it decline downwards.

therefore placing the cylinder perpendicularly, and ſhooting the
ball upwards, it returneth by the ſame right line downwards;
cauſe the motion of the ball dependent on its gravity is
ward, by the ſame perpendicular.
The journey therefore of the
ball out of the piece, continueth or prolongeth the rectitude or
perpendicularity of that ſmall part of the ſaid journey, which it
made within the ſaid piece; is it not ſo?

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