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American Artifacts

C. H. Webb's Machine for Addition

From the Journal of the Franklin Institute, 1870

Machine for Addition.—By C. H. Webb, of New York.— This very simple and efficient piece of mechanism is represented by Fig. 1 in its exterior appearance, and by Fig. 2 as regards its internal mechanism. In the first place, as regards the exterior, A, Fig. 1, represents a plate with 100 holes around its periphery within a divided circle having 100 degrees in its circumference. A small steel point being inserted in one of the holes, enables us to rotate the disk in the direction of the arrow until motion is arrested by the steel point coming to the stop at 0, where the small hand points in the figure. Suppose the disk set with this hand and 0 point of the disk opposite the 0 of the divided circle, and suppose that the steel point is now inserted opposite the figure 10 of the outer circle, and the disk moved until the point strikes the stop. The disk will clearly be moved around a distance corresponding to 10 holes or divisions, and an outer rim of the same which lies under the divided circle, and is numbered from 0 to 99, will show 10 at the open slot between the two circles where 00 is seen in the Fig 1. If, in turn, the steel point is inserted at the point now opposite 15 of the scale, and moved to the stop, the disk will be moved forward by 15 more stops, and the figure exposed at the slot will be 25. When the distance moved forward amounts to 100 divisions and numbers, then, by mechanism to be presently described, the smaller disk to the left advances one step and shows Fig 1 through the same slot in the place for hundreds, the numbers on the larger disk appearing over again in their former order of 0 to 99. The mechanism by which this motion of the second disk is obtained may be seen from Fig. 2. A is a spiral cam which is connected with the disk having the 100 round holes in it, and which being rotated in the direction of the arrow forces the sliding catch,CE, out against the pressure of the spring, F, until a complete revolution is accomplished, when the catch dropping into the re-entrant angle of the cam engages a tooth on the second disk, B, and moves it forward one step or number. There are 50 teeth on B, (although only a few are shown in the cut) corresponding to 50 numbers on the edge of its disk. The highest number which the machine will record is thus 5099, which is, however, quite as much as any column of two figures of average numbers will make, even if it be 100 lines in length. Having added one pair of columns, we then set the disks so as to bring the numbers to be carried into view in the slot, and proceed with the next pair of columns as before. The agency for this instrument, in this city, is in the hands of Messrs. Moss & Co., 432 Chestnut street.

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