Because man had ten fingers and thumbs, he learned to count in tens. When he had counted ten, he could make a mark to remind him of the fact, and then count them over again. Some of the early races learned to designate units from tens and tens from hundreds by working their fingers in various ways. Other peoples also made use of their toes in counting, so that they could count up to twenty without getting bothered. Cantor, the historian, tells of a South African tribe which employed an unusual system of finger counting. Three men sat together facing a fourth who did the counting. Each of the three held up his fingers for the fourth man to count. The first man’s ten fingers and thumbs represented units; the second man represented tens, and the third hundreds. By this means, it was possible to count up to 999. Who Invented the First Adding Machine? Early cuneiform inscriptions, made about 2200 B. C., show that the Babylonians had developed a fairly extensive system of figuring. This was in the days of the patriarch Abraham. When men’s minds were overtaxed with the strain of counting into the hundreds and thousands, the Babylonians invented the first adding machine, a “pebble board,” a ruled surface on which pebbles were shifted about to represent different values. The next adding and calculating machine was an evolution from the digits of the human hand and is known as the abacus in China, and the soroban in Japan. The abacus may be defined as an arrangement of movable beads which slip along fixed rods, indicating by their arrangement some definite numerical quantity. Its most familiar form is in a boxlike arrangement, divided longitudinally by a narrow ridge of two compartments, one of which is roughly some three times larger than the other. Cylindrical rods placed at equal intervals apart pass through the framework and are fixed firmly into the sides. On these rods the counters are beaded. Each counter slides along the rod easily and on each rod there are six tamas or beads. Five of these slide on the longest segment of the rod and the remaining one on the shorter. Addition, subtraction, multiplication, division, and even square and cube root can be performed on the abacus, and in the hands of a skilled operator considerable speed can be obtained. [Illustration: FINGER COUNTING WAS COMMON AMONG EARLIER PEOPLES, AND WAS BROUGHT TO A FAIR DEGREE OF EFFICIENCY BY SOUTH AFRICANS _Courtesy of the Burroughs Adding Machine Company._] [Illustration: THE “ABACUS” WAS ONE OF THE EARLIEST AIDS TO CALCULATION It is still used extensively in China, and occasionally will be found in Chinese laundries in the United States. _Courtesy of the Burroughs Adding Machine Company._]