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

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1ſed to make its vibrations ſucceſſively more and more frequent;
and conſequently is able to bring a continual impediment to the
plummet C; and for a proof that this is ſo, if we do but obſerve
the thread A C, we ſhall ſee it diſtended not directly, but in an
arch; and if inſtead of the thread we take a chain, we ſhall
cern the effect more perſectly; and eſpecially removing the

vity C, to a conſiderable diſtance from the perpendicular A B, for
that the chain being compoſed of many looſe particles, and each of
them of ſome weight, the arches A E C, and A F D, will appear
notably incurvated.
By reaſon therefore, that the parts of the
chain, according as they are neerer to the point A, deſire to make
their vibrations more frequent, they permit not the lower parts of
the ſaid chain to ſwing ſo far as naturally they would: and by
continual detracting from the vibrations of the plummet C, they
finally make it ceaſe to move, although the impediment of the air
might be removed.
The vibrations
of the ſame
dulum are made
with the ſame
quency, whether
they be ſmall or
The cauſe which
impedeth the
dulum, and
ceth it to reſt.
The thread or
chain to which a
pendulum is
ned, maketh an
arch, and doth not
ſtretch it ſelfe
ſtreight out in its
SAGR. The books are now come; here take them Simplicius,
and find the place you are in doubt of.
SIMP. See, here it is where he beginneth to argue againſt the
diurnal motion of the Earth, he having firſt confuted the annual.
Motus terræ annuus aſſerrere Copernicanos cogit converſionem
juſdem quotidianam; alias idem terræ Hemiſphærium continenter
ad Solem eſſet converſum obumbrato ſemper averſo. [In Engliſh
thus:] The annual motion of the Earth doth compell the
pernicans to aſſert the daily converſion thereof; otherwiſe the
ſame Hemiſphere of the Earth would be continually turned
wards the Sun, the ſhady ſide being always averſe.
And ſo one
half of the Earth would never come to ſee the Sun.
SALV. I find at the very ſirſt ſight, that this man hath not rightly
apprehended the Copernican Hypotheſis, for if he had but taken
notice how he alwayes makes the Axis of the terreſtrial Globe
perpetually parallel to it ſelf, he would not have ſaid, that one
half of the Earth would never ſee the Sun, but that the year
would be one entire natural day, that is, that thorow all parts of
the Earth there would be ſix moneths day, and ſix moneths night,
as it now befalleth to the inhabitants under the Pole, but let
this miſtake be forgiven him, and let us come to what
SIMP. It followeth, Hanc autem gyrationem Terræ
poſſibilem eſſe ſic demonſtramus. Which ſpeaks in Engliſh thus:
That this gyration of the Earth is impoſſible we thus demonſtrate.
That which enſueth is the declaration of the following figure,
wherein is delineated many deſcending grave bodies, and
ing light bodies, and birds that fly too and again in the air, &c.
SAGR. Let us ſee them, I pray you. Oh! what fine figures,

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