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

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1of the accelerated degrees of velocity, anſwering to the triangle
A B C, hath paſſed in ſuch a time ſuch a ſpace, it is very reaſonable
and probable, that making uſe of the uniform velocities anſwering
to the parallelogram, it ſhall paſſe with an even motion in the
ſame time a ſpace double to that paſſed by the accelerate
tion.
SAGR. I am entirely ſatisfied. And if you call this a probable
Diſcourſe, what ſhall the neceſſary demonſtrations be?
I wiſh
that in the whole body of common Philoſophy, I could find one
that was but thus
In natural
ences it is not
ceſſary to ſeek
thematicall
dence.
SIMP. It is not neceſſary in natural Philoſophy to ſeek
ſite Mathematical evidence.
SAGR. But this point of motion, is it not a natural queſtion?
and yet I cannot find that Ariſtotle hath demonſtrated any the
leaſt accident of it.
But let us no longer divert our intended
Theme, nor do you fail, I pray you Salviatus, to tell me that
which you hinted to me to be the cauſe of the Pendulum's
eſcence, beſides the reſiſtance of the Medium ro penetration.
SALV. Tell me; of two penduli hanging at unequal
ces, doth not that which is faſtned to the longer threed make its
vibrations more ſeldome?
The pendulum
hanging at a
er threed, maketh
its vibrations more
ſeldome than the
pendulum hanging
at a ſhorter threed.
SAGR. Yes, if they be moved to equall diſtances from their
perpendicularity.
SALV. This greater or leſſe elongation importeth nothing at
all, for the ſame pendulum alwayes maketh its reciprocations in
quall times, be they longer or ſhorter, that is, though the pendulum

be little or much removed from its perpendicularity, and if they
are not abſolutely equal, they are inſenſibly different, as
rience may ſhew you: and though they were very unequal, yet
would they not diſcountenance, but favour our cauſe.

fore let us draw the perpendicular A B [in Fig. 9.] and hang from
the point A, upon the threed A C, a plummet C, and another
on the ſame threed alſo, which let be E, and the threed A C, being
removed from its perpendicularity, and then letting go the
mets C and E, they ſhall move by the arches C B D, E G F, and
the plummet E, as hanging at a leſſer diſtance, and withall, as
(by what you ſaid) leſſe removed, will return back again faſter,
and make its vibrations more frequent than the plummet C, and
therefore ſhall hinder the ſaid plummet C, from running ſo much
farther towards the term D, as it would do, if it were free: and
thus the plummet E bringing unto it in every vibration continuall

impediment, it ſhall finally reduce it to quieſcence.
Now the
ſame threed, (taking away the middle plummet) is a compoſition
of many grave penduli, that is, each of its parts is ſuch a
lum faſtned neerer and neerer to the point A, and therefore