On 7 August 1877, a certain Marshall M. Cram of Mankato, Minnesota, received a United States Patent Nr. 193853 for an adding machine, similar to the later Centigraph of Arthur Shattuck (in contrast with Centigraph however, the device of Cram remained only on paper and never went in serial production).
Like other machines of this kind (so called single column adders, e.g. that of Gonnella), the calculating machine of Cram was intended to add a single digit at a time, i.e. the unit column is entered first, then the tens, the hundreds, the thousands, and so on, certainly rather cumbersome task (as every partial sum had to be recorded on paper and the sum eventually performed), which greatly limits the usefulness of such devices.
Let’s examine the operation and appearance of the calculating machine of Marshall Cram, using the patent drawings (see the lower drawings).
The display capacity of the machine is 999. Overall size: 10 x 18 x 11 cm. Weight: 0.650 kg.
The figures on the slotted indicator scale (marked with c’) indicate hundreds, and those on the periphery of the wheel just above the indicator are units. The operator works the keys with his right hand, the thumb being used on key No. 9. To add a column of figures, a key corresponding to each figure is pressed down as far as it will go, and allowed to rise again before pressing another. After pressing keys to correspond with all the numbers, the sum is read off from the indicator, as shown by the pointer d, and from the wheel just above the indicator. If another column is to be added, set down the right-hand figure, the others being “to carry”; then, pressing the lever (l), turn back the wheel by means of the crank (H), as far as it will go, when the pointer will be at 0 on the indicator, and 0 0 will show on the flanged ratchet wheel (A) with one hundred teeth (a a). Then count first what there was to carry, and proceed with the next column.
It seems the adding machine of Cram remained only on paper, and never went on production. Only one example of the device survived to our time, as it was it preserved by the descendants of the inventor up to the 1990s, when it was sold to Arithmeum Museum in Bonn, Germany (see the upper image). Interestingly, the model in Arithmeum differs somewhat from the patent version: the summing unit is installed on the left (instead of the right) of the keyboard, so obviously this example was made for left-handers.
Biography of Marshall Cram
Almost nothing is known about the inventor of this calculating machine—Marshall Cram.
Marshall Moses Cram was born on 2 June 1853 in Republic, Ohio. He was the youngest child of Moses Bailey Cram (born 17 Oct. 1804 in Weare, New Hampshire—died 18 June 1878 in Faribault, Minnesota), and his first wife Rachel Amanda Cram (Pond) (born 19 Oct 1814 in Shoreham, Vermont—died 1854 in Scipio, Ohio). Moses Bailey Cram and Rachel Amanda Pond married on 18 December 1834, at Madison, Ohio, and had eight children: Martha Arnetta (1836-1917), Rachel Araminta (1838-1869), Abigail (1840-1844), Ellen (1842-1923), Mathilda (1843-1914), Charles (1846-1847), Elvira (1848-1850), and Marshall Moses (1853-1941). After the death of his first wife Rachel Amanda in 1854, Moses Bailey Cram married in 1855 to her younger sister—Lucy Clarinda Pond (1819-1865), and they had three children: Lilly Edith (1856-), Virgil (1858-1901), and Florence (1860-1862).
Besides the above-mentioned patent for a keyboard-driven adding machine, Marshall Cram was a holder of three other US patents (for a boiler cleaner (US634521) and for profile measuring and recording devices (US987863 and US1308580).
Marshall Moses Cram married to Mary Grice (born 1 Oct. 1854 in Pennsylvania—died 25 Nov. 1939 in North Mankato, Minnesota) in 1875 at Minnesota, and they had one daughter—Martha Rubina (1880-1964).
Marshall Moses Cram died died on 16 July 1941 in Minneapolis, Minnesota.