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

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1Earth, like as it carrieth the clouds along with it, ſo it tranſporteth
birds and every thing elſe which is pendent in the ſame; in ſo much
that as to the buſineſſe of keeping pace with the Earth, the birds
need take no care thereof, but for that work might ſleep
SAGR. That the Air can carry the clouds along with it, as
being matters eaſie for their lightneſſe to be moved and deprived
of all other contrary inclination, yea more, as being matters that
partake alſo of the conditions and properties of the Earth; I
prehend without any difficulty; but that birds, which as having
life, may move with a motion quite contrary to the diurnal, once
having ſurceaſed the ſaid motion, the Air ſhould reſtore them to
it, ſeems to me a little ſtrange, and the rather for that they are ſolid
and weighty bodies; and withal, we ſee; as hath been ſaid, ſtones
and other grave bodies to lie unmoved againſt the impetus of the
air; and when they ſuffer themſelves to be overcome thereby,
they never acquire ſo much velocity as the wind which carrieth
SALV. We aſcribe not ſo little force, Sagredus, to the moved
Air, which is able to move and bear before it ſhips full fraught,
to tear up trees by the roots, and overthrow Towers when it
moveth ſwiftly; and yet we cannot ſay that the motion of the
Air in theſe violent operations is neer ſo violent, as that of the
diurnal revolution.
SIMP. You ſee then that the moved Air may alſo cotinue the
motion of projects, according to the Doctrine of Ariſtotle; and
it ſeemed to me very ſtrange that he ſhould have erred in this
SALV. It may without doubt, in caſe it could continue it ſelf,
but lik as when the wind ceaſing neither ſhips go on, nor trees are
blown down, ſo the motion in the Air not continuing after the
ſtone is gone out of the hand, and the Air ceaſing to move, it
followeth that it muſt be ſomething elſe beſides the Air that
keth the projects to move.
SIMP. But how upon the winds being laid, doth the ſhip ceaſe
to move?
Nay you may ſee that when the wind is down, and
the ſails furl'd, the veſſel continueth to run whole miles.
SALV. But this maketh againſt your ſelf Simplicius, for that
the wind being laid that filling the ſails drove on the ſhip, yet
vertheleſſe doth it without help of the medium continue its
SIMP. It might be ſaid that the water was the medium which
carried forward the ſhip, and maintain'd it in motion.
SALV. It might indeed be ſo affirmed, if you would ſpeak
quite contrary to truth; for the truth is, that the water, by

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