Comptograph

Not long after inventing the Comptometer, Dorr E. Felt of Chicago proposed a machine that would print the results of computations. This is an example of that machine, the Comptograph.

The full keyboard printing manual adding machine has a case made out of cherrywood and eight columns of metal keys with white discs in the metal key tops. Digits and complements of digits are indicated on the discs. There are nine keys in each of the eight columns. A spring surrounds each key stem. The cover under the keys is made up of wooden slats with holes drilled in them, with one slat for each column of keys. Slats are alternately of cherry and a lighter-colored wood (possibly beech). In front of the keyboard is a shaped tin plate with 9 windows cut in it to reveal 9 metal wheels that record totals. A row of eight levers above the dials provides decimal markers.

On the right side of the machine toward the front are a knob and a small lever. Depressing the lever allows one to turn the knob and zero the total wheels. To the right of the keyboard is a large button that advances the paper tape and ribbon. This tape and the mechanisms for printing the numbers entered and the totals are behind the keyboard. It appears that only eight-digit totals are printed. The paper tape is set inside a cherrywood lid that folds down when the machine is not in use. A knob on the right side at the back advances the carriage when loading paper. Compare to MA.323633.

According to J. A. V. Turck, a machine of this type was at the National Museum in Washington in 1921. It seems likely that this is the machine he refers to, although the machine pictured by Turck more closely resembles MA.323633, which arrived later.

Reference:

J. A. V. Turck, Origin of Modern Calculating Machines, Chicago: Western Society of Engineers, 1921, pp. 116-120.

Currently not on view