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

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1588000000 yards (for ſo many are in 56 diameters of the Earth)
be paſſed?
The rule for this work is, that the third number muſt
be multiplied by the ſquare of the ſecond, of which doth come
14700000000, which ought to be divided by the firſt, that is, by
100, and the root ſquare of the quotient, that is, 12124 is the
number ſought, namely 12124 min. ſecun. of an hour, which are
3 hours, 22 min. prim. and 4 ſeconds.
SAGR. I have ſeen the working, but I know nothing of the
reaſon for ſo working, nor do I now think it a time to ask it.
SALV. Yet I will give it, though you do not ask it, becauſe it
is very eaſie.
Let us mark theſe three numbers with the Letters
A firſt, B ſecond, C

third.
A and C are the
numbers of the ſpaces,
B is the number of the
time; the fourth number
is ſought, of the time
alſo.
And becauſe we
know, that look what
proportion the ſpace A,
hath to the ſpuace C, the
ſame proportion ſhall the
ſquare of the time B
have to the ſqare of the
time, which is ſought.
Therefore by the Golden Rule, let the number C be
plied by the ſquare of the number B, and let the product be
vided by the number A, and the quotient ſhall be the ſquare of
the number ſought, and its ſquare root ſhall be the number it ſelf
that is ſought.
Now you ſee how eaſie it is to be underſtood.
SAGR. So are all truths, when once they are found out, but the
difficulty lyeth in finding them.
I very well apprehend it, and kindly
thank you.
And if there remain any other curioſity touching this
point, I pray you let us hear it; for if I may ſpeak my mind, I
will with the favour of Simplicius, that from your diſcourſes I
wayes learn ſome new motion, but from thoſe of his
phers, I do not remember that I have learn't any thing of
ment.
SALV. There might be much more ſaid touching theſe local
motions; but according to agreement, we will reſerve it to a
ticular conference, and for the preſent I will ſpeak ſomething
touching the Author named by Simplicius, who thinketh he hath
given a great advantage to the adverſe party in granting that, that
Canon bullet in falling from the concave of the Moon may
ſcend with a velocity equal to the velocity wherewith it would