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

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1of the circle, as a point that was diſtant from the contaction one
palm, and the point that was diſtant half a palm, I likewiſe believe
would ſcarſe recede the fourth part of the diſtance of the ſecond:
fo that within an inch or two of the contact, the ſeparation of the
Tangent from the circumference is ſcarſe diſcernable.
SALV. So that the receſſion of the project from the
rence of the precedent circular motion is very ſmall in the
ing?
SIMP. Almoſt inſenſible.
SALV. Now tell me a little; the project, which from the
tion of the projicient receiveth an impetus of moving along the
Tangent in a right line, and that would keep unto the ſame, did
not its own weight depreſs it downwards, how long is it after the
ſeparation, ere it begin to decline downwards.
SIMP. I believe that it beginneth preſently; for it not
ving any thing to uphold it, its proper gravity cannot but

A grave project,
as ſoon as it is
parated from the
projicient begineth
to decline.
SALV. So that, if that ſame ſtone, which being extruded from
that wheel turn'd about very faſt, had as great a natural
ſion of moving towards the centre of the ſaid wheel, as it hath to
move towards the centre of the Earth, it would be an eaſie
ter for it to return unto the wheel, or rather not to depart from it;
in regard that upon the begining of the ſeparation, the receſſion
ing ſo ſinall, by reaſon of the infinite acuteneſs of the angle of
contact, every very little of inclination that draweth it back
wards the centie of the wheel, would be ſufficient to retain it
on the rim or circumference.
SIMP. I queſtion not, but that if one ſuppoſe that which
ther is, nor can be, to wit, that the inclination of thoſe grave
dies was to go towards the centre of the wheel, they would never
come to be extruded or ſhaken off.
SALV. But I neither do, nor need to ſuppoſe that which is not;
for I will not deny but that the ſtones are extruded.
Yet I ſpeak
this by way of ſuppoſition, to the end that you might grant me
the reſt.
Now fancy to your ſelf, that the Earth is that great
wheel, which moved with ſo great velocity is to extrude the ſtones.
You could tell me very well even now, that the motion of
ction ought to be by that right line which toucheth the Earth in
the point of ſeparation: and this Tangent, how doth it notably
recede from the ſuperficies of the Terreſtrial Globe?
SIMP. I believe, that in a thouſand yards, it will not recede
from the Earth an inch.
SALV. And did you not ſay, that the project being drawn by
its own weight, declineth from the Tangent towards the centre of
the Earth?