Salusbury, Thomas
,
Mathematical collections and translations (Tome I)
,
1667
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is, fifteen firſt minutes of a degree, in one firſt minute of an hour;
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that is, fifteen ſeconds of a degree, in one ſecond of an hour; and
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becauſe one ſecond is the time of the ſhot, therefore in this time
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the Weſtern horizon riſeth fifteen ſeconds of a degree, and ſo
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much likewiſe the mark; and therefore fifteen ſeconds of that
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cle, whoſe ſemidiameter is five hundred paces (for ſo much the
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ſtance of the mark from the Piece was ſuppoſed.) Now let us
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look in the table of Arches and Chords (ſee here is
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Copernicus
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his
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book) what part is the chord of fifteen ſeconds of the
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ter, that is, five hundred paces. </
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>Here you ſee the chord (or
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tenſe) of a firſt minute to be leſs than thirty of thoſe parts, of
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which the ſemidiameter is an hundred thouſand. </
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<
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>Therefore the
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chord of a ſecond minute ſhall be leſs then half of one of thoſe
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parts, that is leſs than one of thoſe parts, of whichthe
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ter is two hundred thouſand; and therefore the chord of fifteen
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conds ſhall be leſs than fifteen of thoſe ſame two hundred thouſand
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parts; but that which is leſs than
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(a)
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fifteen parts of two hun</
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dred thouſand, is alſo more than that which is four centeſmes of
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five hundred; therefore the aſcent of the mark in the time of the
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balls motion is leſſe than four centeſmes, that is, than one twenty
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fifth part of a pace; it ſhall be therefore
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(b)
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about two inches:
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And ſo much conſequently ſhall be the variation of each Weſtern
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ſhot, the Earth being ſuppoſed to have a diurnal motion. </
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<
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>Now if I
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ſhall tell you, that this variation (I mean of falling two inches ſhort
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of what they would do in caſe the Earth did not move) upon
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all doth happen in all ſhots, how will you convince me
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Simplicius,
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ſhewing me by an experiment that it is not ſo? </
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<
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>Do you not ſee
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that it is impoſſible to confute me, unleſs you firſt find out a way
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to ſhoot at a mark with ſo much exactneſſe, as never to miſſe an
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hairs bredth? </
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<
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>For whilſt the ranges of great ſhot conſiſt of
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rent numbers of paces, as
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de facto
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they do, I will affirm that in
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each of thoſe variations there is contained that of two inches
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ſed by the motion of the Earth.</
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(a)
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That is, in
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plainer termes the
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fraction 15/200000, is
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more than the
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ction 4/50000, for
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viding the
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nators by their
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minators, and the
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firſt produceth
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13333 1/3 the other
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but 12500.</
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(b)
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It ſhall be
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neer 2 2/5 inches,
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counting the pace
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to be Geometrical,
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containing 5 foot.</
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<
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>SAGR. </
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>Pardon me,
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Salviatus,
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you are too liberal. </
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<
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>For I would
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tell the
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Peripateticks,
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that though every ſhot ſhould hit the very
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centre of the mark, that ſhould not in the leaſt diſprove the motion
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of the Earth. </
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<
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>For the Gunners are ſo conſtantly imployed in
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velling the ſight and gun to the mark, as that they can hit the ſame,
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notwithſtanding the motion of the Earth. </
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<
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>And I ſay, that if the
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Earth ſhould ſtand ſtill, the ſhots would not prove true; but the
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Occidental would be too low, and the Oriental too high: now let
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Simplicius
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diſprove me if he can.</
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It is
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ted with great
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tilty, that the
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Earths motion
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poſed, Canon ſhot
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ought not to vary
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more than in reſt.
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<
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>SALV. </
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<
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>This is a ſubtilty worthy of
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Sagredus:
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But whether
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this variation be to be obſerved in the motion, or in the reſt of the
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Earth, it muſt needs be very ſmall, it muſt needs be ſwallowed up </
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