Instrument for measuring the area of a plane figure by tracing its boundary line. Two arms that curve towards each other are hinged at the top. One arm has a pin attached at the end, perpendicular to the page, fixing the instrument to the drawing board. Other arm has tracing point at the end. At hinge of arms is a small wheel, axle horizontal to the drawing surface, which rotates at the tracing point is moving along a boundary. The rotation of this wheel also moves a vertical axle dial connected to the small wheel by a gear shaft. The area enclosed by the boundary is read off the wheel and dial. Wheel reads 0-10, by 1/10, with a 0-1 vernier by 1/10. Dial reads 0-10, by one (each ten on the wheel moves the dial one space). A loose lead strip weight is wrapped around the tracer arm. The oblong case is wood covered with reddish-brown leather. Inside is fitted, and lined with purple velvet over cardboard. Case has two hinges on one side, and a catch mechanism for closure. Also in the case is a solid wheel with a screw hole through the center, marked around outside 1-7, by 1/2. Inside measure add reading of plan. to above with proper sign. Area of zero circle with poles inside 148.34 sq. in. Radius 6.871 in.; Measure of opp. wall: cir. (R=2.4 in., R=3.0 in.) both ways with fixed rad. Give for zero.
Inscription/Sig.
"MADE BY/American Steam Gauge Co./Boston, Mass." on case.
