Gravesande, Willem Jacob 's
,
An essay on perspective
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Table of figures
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1 - 30
31 - 60
61 - 82
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31 - 60
61 - 82
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are to be repreſented upon the Paper in the Frame
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G.</
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<
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">43. </
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<
s
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xml:space
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which is repreſented in Fig. </
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<
s
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xml:space
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<
s
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xml:space
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ſuſtain the Box upon its Support or Foot. </
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<
s
xml:id
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xml:space
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">One
<
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of theſe Pieces may be faſtned to one Side of the
<
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Support, and the other to the other Side thereof,
<
lb
/>
by means of four Iron Pins, two of which go thro
<
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the Holes N and P in the Side of the Support,
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and the Holes T and V in the Piece R, and the
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other two in like manner, through Holes made
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in the other Side of the Support, and the other
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Piece, when we have Mind the Bottom of the
<
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Box ſhould be parallel to the Horizon; </
s
>
<
s
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xml:space
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">but when
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the Box is to be a little inclin’d, that Pin going
<
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through the Hole P, muſt be put through the
<
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Hole O, in the Piece R. </
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<
s
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xml:space
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">Underſtand the ſame
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of the other Piece.</
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<
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">44. </
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<
s
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">We are ſometimes obliged to ſet the Box
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forwarder on its Support; </
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<
s
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xml:space
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">and this is done, in
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uſing the Holes Q and S, inſtead of N and P. </
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<
s
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xml:space
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">It
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is likewiſe ſomething neceſſary to incline the
<
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Box a little backwards; </
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<
s
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xml:space
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">which may be done, by
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/>
putting the Pin in S, into the Hole X, made in
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a Piece of Wood faſtned to the Back-ſide of the
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Box, and the correſpondent Pin on the other Side,
<
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/>
into another Hole made on the other Side of the
<
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ſaid Piece.</
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<
s
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xml:space
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">45. </
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<
s
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xml:space
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">The Box ♈ ſlides upon the Top of the
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Machine, and is like that already deſcribed,
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">10, 11,
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13.</
note
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with this Difference only, that it is leſſer. </
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<
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xml:space
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the Top of the Box are two little Staples Z Z,
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in which a Ruler ſlides, having a Mirrour faſtned
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to it, in the Manner as is mentioned Numb. </
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</
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<
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">and ſo by this Means the ſaid Mirrour may be
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put in the ſame Situation, as that in the Figure
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of the firſt Machine it hath in H.</
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