Antiques of Science & Technology

W26-11. Improved Willis Polar Planimeter, Patented 1901 Made by James L. Robertson & Sons New York, this instrument is a fine example of the combination calculator-integrator. By choosing one of six scales on a rotating triangular reader and adjusting the tracing arm, the operator can mechanically "dial in" a constant multiplier to an area from the Planimeter to obtain a direct readout of the quantity desired. For example, the M.E.P. from a steam engine gauge could be measured directly and easily in this manner.
This is a well used instrument, serial number 7042, and incorporates the improved frictionless wheel rotation , see Rittenhouse Journal, Vol. 7, No. 2 article by Hyman Schwartz. The felt lined case has some spotting, the wood 4 x 10 x 1 3/4 in. box is in excellent mechanically shape showing some wear of the cloth covering. This analog instrument is representative of early innovative calculating devices. It took integral calculus which only few people mastered and made it a tool of science and industry.

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