|Salusbury, Thomas Mathematical collections and translations 1667|
hard, as suppose of brass; what think you it would do being let
go? do not you believe (as for my part I do) that it would lie
SIMPL. If that superficies were inclining?
SALV. Yes; for so I have already supposed.
SIMPL. I cannot conceive how it should lie still: nay, I am
confident that it would move towards the declivity with much pro
SALV. Take good heed what you say, Simplicius, for I am
confident that it would lie still in what ever place you should lay
SIMPL. So long as you make use of such suppositions, Sal
viatus, I shall cease to wonder if you inferr most absurd con
SALV. Are you assured, then, that it would freely move to
wards the declivity?
SIMPL. Who doubts it?
SALV. And this you verily believe, not because I told you so,
(for I endeavoured to perswade you to think the contrary) but of
your self, and upon your natural judgment.
SIMPL. Now I see what you would be at; you spoke not this
as really believing the same; but to try me, and to wrest matter
out of my own mouth wherewith to condemn me.
SALV. You are in the right. And how long would that Ball
move, and with what velocity? But take notice that I instanced
in a Ball exactly round, and a plain exquisitely polished, that all
external and accidental impediments might be taken away. And
so would I have you remove all obstructions caused by the Airs re
sistance to division, and all other casual obstacles, if any other
there can be.
SIMPL. I very well understand your meaning, and as to your
demand, I answer, that the Ball would continue to move in in
finitum, if the inclination of the plain should so long last, and con
tinually with an accelerating motion; for such is the nature of
ponderous moveables, that vires acquirant eundo: and the great
er the declivity was, the greater the velocity would be.
SALV. But if one should require that that Ball should move
upwards on that same superficies, do you believe that it would
SIMPL. Not spontaneously; but being drawn, or violently
thrown, it may.
SALV. And in case it were thrust forward by the impression of
some violent impetus from without, what and how great would
its motion be?
SIMPL. The motion would go continually decreasing and re