Salusbury, Thomas
,
Mathematical collections and translations (Tome I)
,
1667
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ball got to the ground, when the little one is ſtill within leſs than
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a yard of the top of the Tower.</
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The error of
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ſtotle
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in affirming,
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falling grave
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dies to move
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ding to the
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tion of their
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ties.
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<
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>SAGR. </
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>That this propoſition is moſt falſe, I make no doubt in
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the world; but yet that yours is abſolutely true, I cannot well
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aſſure my ſelf: nevertheleſs, I believe it, ſeeing that you ſo
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ſolutely affirm it; which I am ſure you would not do, if you had
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not certain experience, or ſome clear demonſtration thereof.</
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<
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>SALV. </
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<
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>I have both: and when we ſhall handle the buſineſs
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of motions apart, I will communicate them: in the interim, that
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we may have no more occaſions of interrupting our diſcourſe, we
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will ſuppoſe, that we are to make our computation upon a ball of
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Iron of an hundred
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(a)
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pounds, the which by reiterated
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ments deſcendeth from the altitude of an hundred
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(b)
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yards, in
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five ſecond-minutes of an hour. </
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>And becauſe, as we have ſaid,
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the ſpaces that are meaſured by the cadent moveable, increaſe in
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double proportion; that is, according to the ſquares of the times,
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being that the time of one firſt-minute is duodecuple to the time
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of five ſeconds, if we multiply the hundred yards by the ſquare of
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12, that is by 144, we ſhall have 14400, which ſhall be the
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ber of yards that the ſame moveable ſhall paſs in one firſt-minute
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of an hour: and following the ſame rule becauſe one hour is 60
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minutes, multiplying 14400, the number of yards paſt in one
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nute, by the ſquare of 60, that is, by 3600, there ſhall come forth
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51840000, the number of yards to be paſſed in an hour, which
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make 17280 miles. </
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<
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>And deſiring to know the ſpace that the ſaid
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ball would paſs in 4 hours, let us multiply 17280 by 16, (which
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is the ſquare of 4) and the product will be 276480 miles: which
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number is much greater than the diſtance from the Lunar concave
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to the centre of the Earth, which is but 196000 miles, making the
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diſtance of the concave 56 ſemidiameters of the Earth, as that
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dern Author doth; and the ſemidiameter of the Earth 3500 miles,
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of 3000 ^{*}
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Braces
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to a †mile, which are our
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Italian
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miles.</
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(a) (b)
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Note that
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theſe Calculations
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are made in
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an
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weights and
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meaſures. </
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<
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>And 100
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pounds
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poiſe
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make 131
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l.
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<
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>Florentine.
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And
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100 Engliſh yards
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makes 150 2/5 Braces
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Florent.
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ſo that the
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brace or yard of
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our
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Author
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is 3/4
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of cur yard.</
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* The
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Italian
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ſure which I
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monly tranſl te
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yards.</
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<
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>Therefore,
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Simplicius,
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that ſpace from the concave of the Moon
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to the centre of the Earth, which your Accomptant ſaid could
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not be paſſed under more than ſix days, you ſee that (computing
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by experience, and not upon the fingers ends) that it ſhall be
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ſed in much leſs than four hours; and making the computation
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exact, it ſhall be paſſed by the moveable in 3 hours, 22
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min. </
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<
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and 4 ſeconds.</
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† The
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Italian
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mile
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is 1000/1056 of our mile.</
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<
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>SAGR. </
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>I beſeech you, dear Sir, do not defraud me of this
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act calculation, for it muſt needs be very excellent.</
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<
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>SALV. </
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<
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>So indeed it is: therefore having (as I have ſaid) by
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diligent tryal obſerved, that ſuch a moveable paſſeth in its deſcent,
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the height of 100 yards in 5 ſeconds of an hour, we will ſay, if
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100 yards are paſſed in 5 ſeconds; in how many ſeconds ſhall </
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