ADDING MACHINES

mechanical devices designed to add, quickly and accurately, long series of figures, date back in idea at least to the 17th century, to Blaise Pascal, a French man. The modern machine fs much more complicated and flexible than the original conception; approximately one hundred modifications of the machine exist in commercial use today. Mast of these are operated by depre ing keys somewhat similar to those of a typewriter. These keys are in groups, of nine numbered from 1 to 9, one group for units, one for tens, one for hundreds and so on for as many places as the machine accommodates. In a listing machine, that is one that prints each item as well as adding them, it is nece ary in addition to depre ing the keys, to pull a lever usually at the right of the machine, or if the machine is electrically operated a button is pushed, which Dili the proper figures on a strip of paper. When the listing is finished the total is printed by pre ing a totalizing key and operating the lever or button as above. Ina non-listing machine the total is read from the figures on the circumference of the wheels described below, which aed through suitable small windows. The mechanism consists of a ‘series of wheels, one for units, one for tens, one for hundreds, etc., corresponding to the number of digits which constitute the capacity of the machine. The circumference of each wheel is divided into ten parts, numbered from 1 to 9 and 0. These wheels are actuated by the keys on the top of the machine, which when depre ed cause the corresponding wheel to turn thru one-tenth, two tenths, three-tenaths of a revolution, depending on whether key 1, 2 or 3 is depre ed. When any wheel makes one full revolution, a projecting tooth or pin on it engages the next higher wheel and causes it to make one-tenth of a turn, thus taking care of carrying.