Mathematical Tables for Use with a Comptometer

The manufacture of computing devices has been associated with mathematical tables at least since the 17th century, when tables of logarithms were used in the manufacture of slide rules. In the mid-19th century, the need for new astronomical tables reportedly inspired the Englishman Charles Babbage to propose a difference engine, which was to print the tables it calculated. The Swedes Georg and Edvard Scheutz actually completed such a machine, and it was used to compute and print tables at the Dudley Observatory in Albany, New York.
The commercially successful adding and calculating machines introduced in the 19th and 20th centuries were used to produce a wide range of tables. At the same time, machine manufacturers supplied their customers with printed tables to assist in routine calculations. These often involved reducing non-metric measurements to decimal portions of a given unit, as these tables suggest.
These six tables, printed on cardboard, were produced for Felt & Tarrant Manufacturing Company of Chicago, manufacturers of an adding machine called the Comptometer. The copyright dates range from 1913 to 1925. All the tables have a photograph of a Comptometer in the upper left corner. Two show the hand and wrist of an operator wearing a suit (presumably a man), and two show the hand and wrist of an operator with a woman’s ring on her finger.
The first table, Felt & Tarrant’s Form No. 8, illustrates the enduring importance of nonmetric measures in American life. It assists in multiplying the number of lengths by a unit length in engineering calculations. The table gives 10, 100, and 1,000 times inches and fractions of an inch to eighths of an inch. Results are given in feet, inches, and fractions of an inch. The table has no copyright date.
The second table, Felt & Tarrant’s Form No. 36, was prepared by one U. S. Edgerton, the only author mentioned on the tables. It was copyrighted in 1913 and is for computing interest, insurance cancellation and discounts, with months and days expressed in decimal equivalents of a year. One side shows a year of twelve 30-day months (360 days total). The other side has a table for days only, that runs from 1 to 364.
The third table, copyrighted in 1914 and 1915, is Felt & Tarrant’s Form 38. It was designed for the textile industry. Entries allow one to reduce drams (of which there 16 to an ounce) and ounces (of which there are 16 to a pound) to decimal portions of a pound. The table has rows for 0 to 15 drams and columns for 0 to 15 ounces.
The fourth table, Felt & Tarrant’s Form 26, was copyrighted in 1917. It indicates the decimal part of a year represented by each date of the month.
The fifth table, Felt & Tarrant’s Form No. 368, shows the decimal equivalents of fractions from thirds to 26ths inclusive. It has no copyright date.
The final table, Felt & Tarrant’s Form No. 386, has measurements in inches, to eighths of an inch, given as decimal portions of a foot. Copyrighted in 1925, it assisted in calculations relating to lumber, steel beams, and angles.
For another table used with the Comptometer, see 2011.3049.01.
Currently not on view
Object Name
mathematical tables
date made
Felt & Tarrant Manufacturing Company
Physical Description
paper (overall material)
overall: .7 cm x 23.6 cm x 25.5 cm; 9/32 in x 9 9/32 in x 10 1/32 in
place made
United States: Illinois, Chicago
ID Number
nonaccession number
catalog number
Science & Mathematics
Mathematical Charts and Tables
See more items in
Medicine and Science: Mathematics
Mathematical Charts and Tables
Data Source
National Museum of American History, Kenneth E. Behring Center
Credit Line
Gift of Oscar W. Richards
Additional Media

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