The practical draughtsman's book of industrial design and machinist's and engineer's companion : forming a complete course of mechanical, engineering and architectural drawing (1866)
Armengaud, M. (Jacques Eugène), 1810-1891, Armengaud, M. (Charles), 1813-1893, Amouroux, M. (Jules), Johnson, William, 1823-1846 · Philadelphia : H.C. Baird · leaf 205
sections. One of the most economically useful instruments of thedraughtsman is the Pentagraph; but it is one which requiressuch extreme accuracy and truthfulness in its construction, thatits consequent cost puts it out of the reach of the majority ofthose who need it. By means of it, drawings may… … pencil by the angular movements of a series of levers oscillatingupon a fixed centre. If one arm of a lever is twice as long as theother, the arc described by its extremity will be twice as great,whatever be the extent of the movement. In this case, howeverthe radii of the arcs would be uniform,…
