[Fig. 174] represents three-leg dividers, used for taking the position of three points; this instrument is very useful in finding the position of a point in a figure.
Fig. 171.—Fig. 172.—Fig. 173.—Fig. 174.
Fig. 175.—Fig. 176.—Fig. 177.—Fig. 178.—Fig. 179.
COMPASSES.
Compasses consist of two pointed legs; they are instruments for describing circles or for—sometimes—measuring figures, in absence of dividers. [Fig. 175] represents compasses fitted as dividers.
Compasses should have jointed legs, which will allow the points to be placed at right angles to the paper, whatever the size of the circle to be drawn. Compasses should not be used for circles which are too large to allow the points to be thus placed; a lengthening bar is generally provided, which greatly increases the diameters of circles which may be drawn by this attachment; it is shown in [fig. 176].
One leg of the compasses is usually provided with a socket to which are fitted three points: a divider point, [fig. 179]; a pencil point, [fig. 177]; and a point, [fig. 178], carrying a special pen for the inking of circles. Each of these points is generally provided with a joint, so that it may be placed at right angles to the paper.
The other leg should be jointed; it is often provided with a socket which receives two points, one a divider point, and the other carrying a needle point. Such an instrument may be used as dividers for spacing, or as compasses for penciling or inking circles.