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

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from
the top of a Tower you let fall a dead bird and a live one,
the
dead bird ſhall do the ſame that a ſtone doth, that is, it ſhall
firſt
follow the general motion diurnal, and then the motion of
deſcent
, as grave; but if the bird let fall, be a live, what ſhall
hinder
it, (there ever remaining in it the diurnal motion) from
ſoaring
by help of its wings to what place of the Horizon it ſhall
pleaſe
?
and this new motion, as being peculiar to the bird, and
not
participated by us, muſt of neceſſity be viſible to us; and if
it
be moved by help of its wings towards the Weſt, what ſhall
hinder
it from returning with a like help of its wings unto the
Tower
.
And, becauſe, in the laſt place, the birds wending its
flight
towards the Weſt was no other than a withdrawing from
the
diurnal motion, (which hath, ſupppoſe ten degrees of velocity)
one
degree onely, there did thereupon remain to the bird whil'ſt
it
was in its flight nine degrees of velocity, and ſo ſoon as it did
alight
upon the the Earth, the ten common degrees returned to it,
to
which, by flying towards the Eaſt it might adde one, and with
thoſe
eleven overtake the Tower.
And in ſhort, if we well
ſider
, and more narrowly examine the effects of the flight of
birds
, they differ from the projects ſhot or thrown to any part of
the
World in nothing, ſave onely that the projects are moved by an
external
projicient, and the birds by an internal principle.
And

here
for a final proof of the nullity of all the experiments before
alledged
, I conceive it now a time and place convenient to
demonſtrate
a way how to make an exact trial of them all.
Shut your ſelf up with ſome friend in the grand Cabbin between
the
decks of ſome large Ship, and there procure gnats, flies, and
ſuch
other ſmall winged creatures: get alſo a great tub (or
other
veſſel) full of water, and within it put certain fiſhes; let
alſo
a certain bottle be hung up, which drop by drop letteth forth
its
water into another bottle placed underneath, having a narrow
neck
: and, the Ship lying ſtill, obſerve diligently how thoſe ſmall
winged
animals fly with like velocity towards all parts of the
bin
; how the fiſhes ſwim indifferently towards all ſides; and how
the
diſtilling drops all fall into the bottle placed underneath.
And
caſting
any thing towards your friend, you need not throw it with
more
force one way then another, provided the diſtances be equal:
and
leaping, as the ſaying is, with your feet cloſed, you will reach

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