[1807]. Cyclograph, for describing arcs, the chord and versed sine being given. Fix pins at A and B, fasten together at C two slips of wood, hold the pencil at D, and move the slips round, keeping them against the pins. See also [No. 11].
[1808]. Hyperbolagraph. Height and focus are given as for [1809], and string fixed to B, and focus A; the arm is pivoted at C, and the pencil used as described for [No. 1809].
[1809]. Parabolagraph. The height of parabolic curve H and focus A are given. A string is fastened to end of set square at B, reaching to C, and the other end fixed to a pin in the focus A. A pencil held in the loop and kept against edge of set square as it is moved to left or right will describe the parabolic curve.
[1810]. Cycloidograph, describes the hypo- or epi-cycloid. A modification of this is used to draw the curves of the teeth of wheels.
Pentagraph, for reducing or enlarging outline drawings, [No. 1924].
Helicograph, to describe a regular helix by a central fixed bevil wheel which drives the radial bevil wheel screw and scribing pencil, [No. 1925].
A simple helicograph, with radial screw and roller nut, which travels along the screw as the apparatus is revolved on its centre pin, [No. 1926].
Section 99.—MATERIALS EMPLOYED IN CONSTRUCTION
The following memoranda relate only to such materials as are required in connection with machinery or mechanical constructions, and are intended to supply particulars of the dimensions of the manufactured or raw material, giving the sections manufactured and the limits as to size available for incorporation in any design under consideration.