Adding MachinesFull-Keyboard – Hill to Felt & Tarrant
In the mid-19th century, the Unitarian minister, mathematician and inventor Thomas Hill envisioned an adding machine that would have a column of keys for each digit entered. Hill took out a U.S. Patent for the device, but it never became a practical product.
Almost thirty years later, Chicago machinist Dorr E. Felt (1862-1930) decided to design an improved adding machine for accountants. Like Victor Schilt, he was interested in adding machines with keys, but he wanted to add larger numbers and to add them quickly. To do this, he devised a machine with several columns of keys. In each column, the keys were numbered from 1 to 9. The column as a whole represented one digit of a number. Felt first made a crude model using a macaroni box from a local grocer, with meat skewers for key stems and rubber bands for screws. He built several prototypes of the machine, and named it the Comptometer. Felt also soon built a printing version of the machine, which he called the Comptograph. It never sold widely.
On Felt’s Comptometer, pushing a key not only set up a digit, but entered it into the mechanism. Felt carefully cultivated customers, and won the financial support of Robert Tarrant as well as orders from government offices, businesses, and scientific observatories. Felt & Tarrant Manufacturing Company sent its products overseas as well as across the country. It built special Comptometers for adding fractions and non-decimal currency, and steadily improved, but did not radically alter, the product. Felt & Tarrant used some of its profits to acquire adding machines of historic interest.
Felt died in 1930. After considerable debate, descendents of Felt and Tarrant decided to take the firm public in 1946, taking the name Comptometer Corporation. The postwar years proved difficult, especially for foreign sales. In 1961, the firm merged with the Victor Adding Machine Company of Chicago to form Victor Comptometer Corporation. The products of this company looked quite different from those of Felt & Tarrant, as they were ten-key, printing machines. Not long thereafter, Victor Comptometer donated Felt’s collection of historically important machines to the Smithsonian.
"Adding Machines - Full-Keyboard – Hill to Felt & Tarrant" showing 1 items.
- This U.S. Patent Office model for an early key-driven adding machine has a wooden case with two columns of keys. Each collumn has six wooden keys. At the back are two wooden discs. Around the edge of each disc is a paper slip with the digits from 0 to 9 printed. These digits repeat seven times on each disc. To the right of each digit is, in smaller type, its nines complement, which is used in subtraction and division. Each wheel of the machine has attached to its side a ratchet that rotates according to the motion of a pawl. The base of the pawl is attached to the end of a lever that extends forward the length of the machine and is pivoted near the front. Above each lever, on the outside of the machine, is a column of keys, numbered from 1 at the top to 6 at the bottom.
- To enter a number, the user depressed a key, which depressed the lever and moved the pawl, rotating the ratchet and wheel forward. Each wheel also had a toothed disc attached to it. After the wheel rotated forward past a "9" position, a tooth on the disc encountered a metal arm which drove a pawl on the adjacent wheel forward one position, causing a carry.
- Thomas Hill, who took out a patent on this machine, was a Unitarian minister and, for a time, president of Harvard University. This patent did not result in a product.
- Thomas Hill, "Improved Arithmometer," U.S. Patent 18692, November 24, 1857.
- Thomas Hill, "On a New Form of Arithmetical Complements," Proceedings of the American Association for the Advancement of Science, 1857, 11:82;
- J. A. V. Turck, Origin of Modern Calculating Machines, Chicago: The Western Society of Engineers, 1921, pp. 22-29, 61-62.
- P. A. Kidwell, “Thomas Hill: Minister, Intellectual and Inventor,” Rittenhouse, 12 (October 1998): pp. 111-119.
- Currently not on view
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- Hill, Thomas
- Hill, Thomas
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- Data Source
- National Museum of American History, Kenneth E. Behring Center