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

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SALV. I have both: and when we ſhall handle the buſineſs
of
motions apart, I will communicate them: in the interim, that
we
may have no more occaſions of interrupting our diſcourſe, we
will
ſuppoſe, that we are to make our computation upon a ball of

Iron
of an hundred (a) pounds, the which by reiterated
ments
deſcendeth from the altitude of an hundred (b) yards, in
five
ſecond-minutes of an hour.
And becauſe, as we have ſaid,
the
ſpaces that are meaſured by the cadent moveable, increaſe in
double
proportion; that is, according to the ſquares of the times,
being
that the time of one firſt-minute is duodecuple to the time
of
five ſeconds, if we multiply the hundred yards by the ſquare of
12
, that is by 144, we ſhall have 14400, which ſhall be the
ber
of yards that the ſame moveable ſhall paſs in one firſt-minute
of
an hour: and following the ſame rule becauſe one hour is 60
minutes
, multiplying 14400, the number of yards paſt in one
nute
, by the ſquare of 60, that is, by 3600, there ſhall come forth
51840000
, the number of yards to be paſſed in an hour, which
make
17280 miles.
And deſiring to know the ſpace that the ſaid
ball
would paſs in 4 hours, let us multiply 17280 by 16, (which
is
the ſquare of 4) and the product will be 276480 miles: which
number
is much greater than the diſtance from the Lunar concave
to
the centre of the Earth, which is but 196000 miles, making the
diſtance
of the concave 56 ſemidiameters of the Earth, as that
dern
Author doth; and the ſemidiameter of the Earth 3500 miles,

of
3000 ^{*}Braces to a †mile, which are our Italian miles.
* The Italian
ſure
which I
monly
tranſl te
yards
.
The Italian mile
is
1000/1056 of our mile.

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