GB190309095A - Improvements relating to Mathematical Calculating Devices. - Google Patents

Abstract

9095. Anderson, F. J. April 22. Slide rules. - A long scale for a common logarithmic slide rule is broken up into parts of equal length, each representing numbers between consecutive integral powers of some chosen power of 10, these parts being placed as parallel scale s, one above the other, upon the two limbs or edges of the rule, the slider being similarly divided. In operating, addition or subtraction of numbers borne by the scales produces the number of the scale upon which the result will be found with the decimal point in the correct position, in a manner analogous to the use of the characteristics of logarithms. The graduations of the scales upon one limb are twice the size of those upon the other, whereby numbers may be squared and cubed, or the corresponding roots taken. Fig. 4 shows a rule with an upper limb A divided into parts representing numbers from 1 to #10, #10 to 10, and so on, a similar slide B, and a lower limb with double length graduations, i.e., with sections from 1 to <4>#10, <4>#10 to #10, and so on, these graduations thus representing, in position, the logarithms of the squares of the same numbers on the upper limb. Fig. 7 shows a glass cursor and frame, bearing the characteristic numbers A', B<1>, C' of the three scales, corresponding numbers appearing upon transverse index bars, Fig. 8, borne one at each end of the slide. In multiplying, the left or right index of the slide is placed against one factor on the upper limb, and the product found on the same limb exactly over the reading of the other factor on the slide. The characteristic number of the product scale is the sum of the two factor scales in the case of the left index, or the sum increased by unity in the case of the right index. Similar rules hold for other operations. Slides with trigonometrical and other scales may be used, and constants specially marked upon the limbs, colours being, preferably, used to distinguish unit from subdivision marks. The arrangement renders any system of subdividing the units possible.