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Per-spec′tive-instru-ment.

A mechanical contrivance to assist persons in drawing in perspective.

A camera-lucida or camera-obscura will enable a perspective delineation. See camera-lucida; camera-obscura.

Bevis's perspective-instrument, described by Ferguson, consists of a rectangular board with a hinged movable frame of an arched shape, and having two adjustable strings, which may be made to intersect each other and assume any direction. The eye steadily beholding an object, say the pediment of a building, the strings are brought into coincidence with the required lines of the object; the frame is then laid down on the board, the point or lines marked on the paper, and, the frame being raised, another point or line is observed and similarly transferred to the paper. The observations are taken through an eye-piece, [1672] which may be approached to or receded from the frame, according to the scale of the drawing required.

Ronalds's perspective-machine, patented in England, has an eye-piece and an arrangement by which a bead traversing in the plane of delineations is made to confer a corresponding motion upon a pencil.

A perspective-instrument for drawing the outlines of any object in perspective was invented by Dr. Christopher Wren, about 1669, and is described in the “Abridgment of Phil. Trans.,” Vol. I. p. 325.

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Christopher Wren (1)
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