Galilei, Galileo, The systems of the world, 1661

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1turn round, ſtaying there above, and moving along with the
urnal
converſion.
Now I tell him, that that ſame ball falling from
the
concave unto the centre, will acquire a degree of velocity
much
more than double the velocity of the diurnal motion of the
Lunar
concave; and this I will make out by ſolid and not

tinent
ſuppoſitions.
You muſt know therefore that the grave
body
falling and acquiring all the way new velocity according
to
the proportion already mentioned, hath in any whatſoever
place
of the line of its motion ſuch a degree of velocity, that if it
ſhould
continue to move therewith, uniformly without farther
encreaſing
it; in another time like to that of its deſcent, it would
paſſe
a ſpace double to that paſſed in the line of the precedent
motion
of deſcent.
And thus for example, if that ball in coming
from
the concave of the Moon to its centre hath ſpent three hours,
22
min. prim. and 4 ſeconds, I ſay, that being arrived at the
tre
, it ſhall find it ſelf conſtituted in ſuch a degree of velocity, that
if
with that, without farther encreaſing it, it ſhould continue to
move
uniformly, it would in other 3 hours, 22 min. prim. and
4
ſeconds, paſſe double that ſpace, namely as much as the whole
diameter
of the Lunar Orb; and becauſe from the Moons
cave
to the centre are 196000 miles, which the ball paſſeth in 3
hours
22 prim. min. and 4 ſeconds, therefore (according to what
hath
been ſaid) the ball continuing to move with the velocity
which
it is found to have in its arrival at the centre, it would
paſſe
in other 3 hours 22 min.
prim. and 4 ſeconds, a ſpace
ble
to that, namely 392000 miles; but the ſame continuing in
the
concave of the Moon, which is in circuit 1232000 miles, and
moving
therewith in a diurnal motion, it would make in the ſame
time
, that is in 3 hours 22 min.
prim. and 4 ſeconds, 172880
miles
, which are fewer by many than the half of the 392000
miles
.
You ſee then that the motion in the concave is not as the
modern
Author ſaith, that is, of a velocity impoſſible for the
ing
ball to partake of, &c.

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