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

Table of figures

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              <s>
                <pb xlink:href="040/01/912.jpg" pagenum="219"/>
                <emph type="italics"/>
              to be the Altitude, and C B the Amplitude of the Semiparabola A B;
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              which is deſcribed by the Compoſition of two Lations; of which one is
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              that of the Moveable deſcending along A C with a Motion Naturally
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              Acceler ate
                <emph.end type="italics"/>
              ex quiete
                <emph type="italics"/>
              in A; the other is the Equable Tranſverſal Moti­
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              on according to the Horizontal Line A D. The
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              Impetus
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              acquired in C
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              along the Deſcent A C is determined by the quantity of the ſaid height
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              A C; for the
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              Impetus
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              of a Moveable
                <emph.end type="italics"/>
                <lb/>
                <figure id="id.040.01.912.1.jpg" xlink:href="040/01/912/1.jpg" number="149"/>
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                <emph type="italics"/>
              falling from the ſame height is alwaies
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              one and the ſame: but in the Horizontal
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              Line one may aſſign not one, but innume­
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              rable Degrees of Velocities of Equable
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              Motions: out of which multitude that I
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              may ſingle out, and as it were point with
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              the finger to that which I make choice of,
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              I extend or prolong the Altitude C A
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              in
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              ſublimi,
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              in which, as was done before, I
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              will pitch upon A E; from which if I
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              conceive in my mind a Moveable to fall
                <emph.end type="italics"/>
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              ex quiete
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              in E, it appeareth that its
                <emph.end type="italics"/>
              Im­
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              petus
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              acquired in the Time A, is one with which I conceive the ſame
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              Moveable being turned along A D to be moved; and its degree of
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              Vclocity to be that, which in the Time of the Deſcent along E A paſſeth
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              a Space in the Horizon double to the ſaid E A. </s>
              <s>This Præmonition I
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              judged neceſſary.
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              </s>
            </p>
            <p type="main">
              <s>
                <emph type="italics"/>
              It is moreover to be advertized that the Amplitude of the Semi­
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              parabola A B ſhall be called by me the Horizontal Line
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              [or Plane]
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                <emph type="italics"/>
              C B.
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              </s>
            </p>
            <p type="main">
              <s>
                <emph type="italics"/>
              The Altitude, to with A C, the Axis of the ſaid Parabola.
                <emph.end type="italics"/>
              </s>
            </p>
            <p type="main">
              <s>
                <emph type="italics"/>
              And the Line E A, by whoſe Deſcent the Horizontal
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              Impetus
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              is de­
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              termined, I call the Sublimity, or height.
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              </s>
            </p>
            <p type="main">
              <s>
                <emph type="italics"/>
              Theſe things being declared and defined, I proceed to Demonſtra­
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              tion.
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              </s>
            </p>
            <p type="main">
              <s>SAGR. Stay, I pray you, for here me thinks it is convenient to
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              adorn this Opinion of our Author with the conformity of it to
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              the Conceit of
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              Plato
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              about the determining the different Veloci­
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              ties of the Equable Motions of the Revolutions of the Cœleſtial
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              Bodies; who, having perhaps had a conjecture that no Moveable
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              could paſſe from Reſt into any determinate degree of Velocity in
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              which it ought afterwards to be perpetuated, unleſs by paſſing
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              thorow all the other leſſer degrees of Velocity, or, if you will,
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              greater degrees of Tardity, which interpoſe between the aſſigned
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              degree, and the higheſt degree of Tardity, that is of Reſt, ſaid that
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              God after he had created the Moveable Cœleſtial
                <emph type="italics"/>
              B
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              odies that he
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              might aſſign them thoſe Velocities wherewith they were afterwards </s>
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