Salusbury, Thomas
,
Mathematical collections and translations (Tome I)
,
1667
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degrees. </
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>Which may the better be ſeen, by hanging two weights
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at two ſtrings of equal length, and then removing them from
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pendicularity, one a little way, and the other very far; the which
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being ſet at liberty, will go & return under the ſame times, the one
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by arches very ſmall, & the other by very great ones, from whence
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followeth the concluſion of an admirable Problem; which is,
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That a Quadrant of a Circle being given (take a little diagram of
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the ſame, [in
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Fig.
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3.]) as for inſtance: A B erect to the Hori
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zon, ſo as that it reſt upon the plain touching in the point B. and
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an Arch being made with a Hoop well plained and ſmoothed in
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the concave part, bending it according to the curvity of the
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cumference A D B. </
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>So that a Bullet very round and ſmooth
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may freely run to and again within it (the rim of a Sieve is very
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proper for the experiment) I ſay, that the Bullet being put in any
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what ever place, neer or far from the loweſt term B. </
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>As for
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ſtance, putting it in the point C, or here in D, or in E; and then
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let go, it will in equal times, or inſenſibly different arrive at the
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term B, departing from C, or from D, or from E, or from
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ever other place; an accident truly wonderfull. </
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>We may add
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another accident no leſs ſtrange than this, which is, That
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over by all the cords drawn from the point B to the points C,
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D, E; and to any other whatſoever, taken not onely in the
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drant B A, but in all the whole circumference of the Circle the
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ſaid moveable ſhall deſcend in times abſolutely equal; inſomuch
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that it ſhall be no longer in deſcending by the whole Diameter
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erect perpendicularly upon the point B, then it ſhall in
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ing by B. C. although it do ſublend but one ſole degree, or a
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ſer Arch. </
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>Let us add the other wonder, which is, That the
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tions of the falling bodies made by the Arches of the Quadrant
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A B; are made in ſhorter times than thoſe that are made by the
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cords of thoſe ſame Arches; ſo that the ſwifteſt motion, and
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made by a moveable in the ſhorteſt time, to arrive from the
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point A, to the term B, ſhall be that which is made, not by the
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right line A, B, (although it be the ſhorteſt of all thoſe that can
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de drawn between the points A. B.) but by the circumference
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A D B. </
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<
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>And any point being taken in the ſaid Arch; as for
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example: The point D. and two cords drawn A D, and D. B.
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the moveable departing from the qoint A, ſhall in a leſs time
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come to B, moving by the two cords A D and D B. than by the
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ſole cord A, B. </
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<
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>But the ſhorteſt of all the times ſhall be that of
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the fall by the Arch A D B. </
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<
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>And the ſelf ſame accidents are
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to be underſtood of all the other leſſer Arches taken from the
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lowermoſt term B. upwards.</
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The ſecond
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ample.
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Two particular
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notable accidents
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in the
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penduli
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and
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their vibrations.
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Admirable
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blems of
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bles deſcending by
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the Quadrant of a
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Circle, and of thoſe
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deſcending by all
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the cords of the
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whole Circle.
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<
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>SAGR. </
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<
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>No more, no more; for you ſo confund and fill me
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with Wonders, and diſtract my thoughts ſo many ſeveral wayes, </
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