A slide-rule adapted for english monetary calculations

摘要

621,148. Calculating- apparatus. PARKES, A. W. Aug. 3, 1946, No. 23190. [Class 106 (i)] A calculator for problems involving English monetary units comprises two relatively movable members, one bearing a scale of numbers and percentages arranged logarithmically and the other bearing a logarithmic scale of monetary values subdivided into three or more parts extending from end to end across the width of the member. Fig. 1 shows a slide-rule comprising a stock bearing a money scale extending from “d. to ú100, marked in accordance with the logarithms of the decimal equivalents of ú1 and subdivided into five parts, and a slide bearing a number and per cents scale extending from 1 to 10, marked logarithmically The part of the logarithmic money scale from “d. to 2¢d. is repeated in decimals of 1d. The number scale 1 to 10 may be expanded and arranged in a double or treble row or contracted and arranged in half a row and then extended to 100, with consequent expansion or contraction and rearrangement of the money scale. Supplementary money and number scales extending from “d. to ú1000 and from 1 to 100,000 may be added for calculating approximate answers to give the order of magnitude of the result required. A logarithmic number scale may be added to the stock and a logarithmic money scale may be added to the slide for pure number problems and "rates in the pound " problems respectively. To avoid the necessity of resetting the slide in certain problems, the number scale may be continued to double length or repeated twice. Special marks may indicate numbers frequently used and a cursor a may be provided. The money and number scales could be marked round relatively movable discs or drums to form disc or drum calculators respectively, suitable registering means being provided. Specification 621,133 is referred to.