Pantograph, or PANTOGRAPHER, an instrument designed for drawing figures in what proportion you please, without any skill in the art.

The instrument is otherwise called a parallelogram.

The following is the description of this instrument by Mr Adams.

"It is an instrument (says Mr Adams) as useful to the experienced draftsman, as to those who have made but little progress in the art. It saves a great deal of time, either in reducing, enlarging, or copying of the same size, giving the outlines of any drawing, however crooked or complex, with the utmost exactness; nor is it confined to any particular kind, but may with equal facility be used for copying figures, plans, sea-charts, maps, profiles, landscapes, &c.

Description and use of the Pantographer.—I have not been able to ascertain who was the inventor of this useful instrument. The earliest account I find is that of the Jesuit Scheiner, about the year 1631, in a small tract entitled Pantographicus, sive ars nova delineandi. The principles are self-evident to every geometrician; the mechanical construction was first improved and brought to its present state of perfection by my father, about the year 1750. It is one, among many other scientific improvements and inventions completed by him, that others have ingloriously, and many years after, assumed to themselves.

"The pantographer is usually made of wood, or brass, and consists of four flat rules, two of them long, and two short. The two longest are joined at the end A, by a double pivot, which is fixed to one of the rules, and works in two small holes placed at the end of the other. Under the joint is an ivory castor, to support this end of the instrument. The two smaller rules are fixed by pivots at E and H, near the middle of the larger rules, and are also joined together at their other end, G.

"By the construction of this instrument, the four rules always form a parallelogram. There is a sliding box on the longer arm, and another on the shorter arm. These boxes may be fixed at any part of the rules by means of their milled nuts; each of these boxes is furnished with a cylindric tube, to carry either the tracing point or crayon or fulcrum.

"The fulcrum or support K, is a leaden weight inclosed in a mahogany box, on this the instrument moves when in use; there are two moveable rollers, to support and facilitate the motions of the pantographer; their situation may be varied as occasion requires.

"The graduations are placed on two of the rules; on each of them are two scales, the fiducial edges of the boxes are to be set to these, according to the work to be performed by the instrument.

"The crayon, the tracer, and fulcrum, must in all cases be in a right line, so that when they are set, if a string be stretched over them, and they do not coincide with it, there is an error either in the setting or graduations.

"The long tube which carries the pencil or crayon, moves easily up or down another tube; there is a string affixed to the long or inner tube, passing afterwards through the holes in the three small knobs to the tracing point, where it may, if necessary, be fastened. By pulling this string, the pencil is lifted up occasionally, and thus prevented from making false or improper marks upon the copy.

"To use this instrument when the copy is to be of the same size as the original.—Place the instrument upon a large table, and set the sliding boxes B and D, to the divisions marked 12. Put the crayon into the box B, place the box D upon the fulcrum or leaden foot; the tracing point at C. Then lay a piece of paper under the crayon, and the original drawing under the tracer, and move the tracing point over the principal strokes of the original, and the crayon will form the required copy.

"To reduce a drawing, &c., to half the size of the original.—Set the boxes B and D, to the divisions marked one-half, place the fulcrum at B, the crayon at D, and tracer at C.

"To reduce a drawing, &c., to less than one-half the original.—Suppose one-third, one-fourth, one-fifth, &c. Place the fulcrum at B, crayon at D, and tracer at C, and slide the boxes B and D, to the divisions marked one-third, one-fourth, one-fifth, &c. on the longer scales. It may be proper to observe here, that if the copy be less than one-half the original, or when it is required greater than the original, the longer scales are to be used.

"For greater than one-half the original drawing.—Suppose it be required to make a drawing, two-thirds three-fourths, four-fifths, &c. Set the boxes B and D, to corresponding divisions, as two-thirds, three-fourths, four-fifths, &c. on the shorter scales, place the fulcrum at D, the crayon at B, and tracer at C.

"When the original drawing is to be enlarged.—Suppose one-eighth, one sixth, &c. set the boxes B and D, to one-eighth, one-sixth, &c. on the longer scales, place the fulcrum at D, the crayon at C, and tracer at B.

"Where the copy is required of a size differing from the fractional parts laid down on the instrument.—For this purpose there are two scales laid down, containing 100 unequal parts, one scale numbered from 10 to 80, the other from 50 to 100.

"If the copy is to be under one-half the original size, place the boxes B and D, to any two corresponding divisions under 50, the fulcrum at B, and crayon at D.

"If the copy is to be larger than one-half the original, place the boxes B and D, to corresponding divisions between 50 and 100; the fulcrum at B, and crayon at D.

"To change the situation of the pantographer.—Copy first as much as the pantographer will take in; then make three points on the original, and as many corresponding points on the copy. Then remove the fulcrum to another situation, but so, that when the tracing point is applied to the three points marked on the original, the crayon may exactly coincide with the other three points on the copy, and proceed as before; and so on for every change in the situation of your instrument, and by this means a pantographer of two feet and a half in length will copy a drawing of any size whatsoever."