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

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1hard, 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
ſtill?
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
penſneſs.
SALV. Take good heed what you ſay, Simplicius, for I am
confident that it would lie ſtill in what ever place you ſhould lay
it.
SIMPL. So long as you make uſe of ſuch ſuppoſitions,
viatus, I ſhall ceaſe to wonder if you inferr moſt abſurd
cluſions.
SALV. Are you aſſured, then, that it would freely move
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
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
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
finitum, if the inclination of the plain ſhould ſo long laſt, and
tinually with an accelerating motion; for ſuch is the nature of
ponderous moveables, that vires acquirant eundo: and the
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
ſo do?
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