London: Charles Griffin, 1908. First edition. Calculator on varnished thick card with three moving circular pieces of graduating size fastenedat the center with a brass rivet on a back-board (this measuring 6.5 inches square),with an accompanying text of 12 pages, stitched, as issued, all in fine condition, inoriginal slim cardboard box. It is unusual for such a comparatively earlycomputing machine to have survived in this condition. Item #7379
“The computer is an ingenious form of mechanical calculator for solving the numerousproblems connected with the power, size, and speed of steam engines of all kinds. Its action isbased upon the well-known principle of logarithmic calculation, the operations ofmultiplication and long division being effected mechanically by the addition and subtraction ofdistances proportional to the logarithms of the quantities represented...” (Introduction).