Gravesande, Willem Jacob 's
,
An essay on perspective
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224
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on PERSPECTIVE.
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<
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">46. </
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<
s
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xml:space
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">When we have a mind to remove this
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Machine from one place to another, we lay the
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Box B E C upon the croſs Pieces 2, 3, 4, 5, with
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its opening A B C upwards; </
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<
s
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xml:space
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">then we put the
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little Box Y, the Ruler and Mirrour (mentioned
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Numb. </
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<
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">13.) </
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<
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">the black Cloth, and the two Sticks
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M L and I H, all into the ſaid great Box; </
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<
s
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xml:space
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">and
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afterwards partly cover it by the Frame G,
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xlink:label
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">40.</
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which is ſuſtained by two very thin Rulers, and
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then by another little Board, when the Frame is
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not big enough. </
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<
s
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xml:space
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">The whole Machine thus taken
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to pieces, will take up no more room than the
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Support itſelf doth: </
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<
s
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xml:space
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">and ſo it is very eaſy to re-
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move from Place to Place. </
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<
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xml:space
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">Now when Objects
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are to be repreſented in this Machine, it muſt be
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put together again, as per Figure; </
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<
s
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xml:space
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">and the black
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Cloth, for a Perſon to put his Head under, hang-
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ing upon the Sticks, and faſtned to the Sides of
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the opening A B, A C, and C D.</
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">The Uſe of this Machine.</
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<
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">47. </
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<
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">The Uſe of this Second Machine is the
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fame as that of the Firſt; </
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<
s
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xml:space
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">but it ought to be ob-
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ſerved, that when we incline the Machine,
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xlink:label
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">43.</
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Angle of Inclination of the Mirrour and Hori-
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zon muſt be made leſs, by half the Inclination of
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the Bottom of the Box; </
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<
s
xml:id
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xml:space
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">and when the Machine
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is ſomewhat inclin’d backwards, the ſaid
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muſt be made greater by a like half. </
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<
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likewiſe obſerve, that when Objects are to be
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repreſented for a perpendicular Picture, the Ma-
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chine muſt be placed according to the former
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Part of Numb. </
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<
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<
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xml:space
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">Prints muſt be faſtned to a
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Board entirely ſeparated from the Machine, which
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Board muſt be ſet upon a Support, that may
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conveniently be moved backwards or forwards,
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according to Neceſſity.</
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