In February 1876 David Carroll, a self-taught inventor of Spring Creek, Pennsylvania, filed a patent application for an adding machine. The patent was granted on 2 May 1876 US Patent №176833 (see the nearby patent drawing). The machine of Carroll seems like well well-designed and workable device, but obviously never went into production, and only the patent model (see the lower image) survived to the present time (property of Smithsonian National Museum).
The adding device of Carroll was a simple single-column adder (column adders can have two or more result digits, but you can only add into the rightmost digit, and then generally only with the integers one through nine). It was made of wood and metal, with measurements: 10.8 cm x 12 cm x 18 cm.
The mechanical calculator of Carroll is a small nine-key 3 positional adding machine. It has a wooden case with nine metal keys with wooden key covers, arranged in two rows—2 4 6 8 (upper row) and 1 3 5 7 9. There are three wooden numeral wheels visible through a window at the top of the box.
The machine is designed to add single digits up to 999. The effect of the keys is determined by the adjusting screws (marked with G on the patent drawing) on the underside of the machine. The keys are constructed as to length, so that when knobs (H) are pushed down to the top of the case, they turn the wheel the number of teeth, corresponding to the number of the key.
The three registering wheels have on their left side a ring of ten equidistant pins, that are used in carrying. There is a lever at the top of the machine, that can be adjusted to release the number wheels so that they can be turned back to zero using the turn-knob (V) on the left.
There is a fixing mechanism provided, to prevent the main wheel from turning too far when the keys are pressed. It consists of a stop-pawl (I), which engages ratchet-wheel (J) at the moment the pawl (E) stops in the downward movement.
Biography of David Carroll
David Carroll was born on 13 May 1828, in the old homestead farm of William Carroll (12 May 1796–24 Dec 1882) and his wife Hannah Slawson-Carroll (30 Jun 1800–8 Jan 1873), located 2 1/2 Miles S.W. of Union City, Erie County, Pennsylvania. David was the third child (of nine) in the family and had four brothers and four sisters.
David’s grandfather, Ferdinand Carroll (1751-1831), in the spring of 1801, embarked after eight weary weeks from Dublin to New Castle, Delaware, in an old war vessel, with his wife Isabella Johnston Carroll (1755-1830) and five sons and four daughters (of twelve children, as two of them died in Ireland, one died of measles during the voyage and was buried at sea). The family and all their earthly possessions came to Union Township on horseback from Pittsburgh in the fall of 1801 and they built their first small home from poles and called it Castle Halsey. William, his youngest son, was to become David’s father.
David Carroll was a diligent schoolboy, always winning prizes. Mathematics was his best subject and he was always far ahead of his classmates. But despite his talent in mathematics, science was his favorite subject.
David’s interests in science and his mechanical aptitude, inherited from his father, led him to become an inventor. He could picture in his mind the dimensions of every separate piece of machinery and how it would look put together. When he was still a boy he conducted perpetual motion studies.
In the US census, David Carroll is listed as a carpenter (the year 1850), farmer (1860 and 1870), and inventor (1880). He married in 1854 to Elizabeth Coventry-Carroll (b. 1832 in England-d. 5 Jun 1891). The family had nine children—Ellen (b. 1855), Jennie Blanche (1860-1947), Rosannah (b. 1862), Etta (b. 1868), Freddie (b. 1870), Hannah (b. 1873), George (1875-1885), Girta May (b. 1878), and Rose A. (1881-1885).
However, David Carroll’s most important invention was not the adding machine, interesting to us, but his Leway ship log, which proved to be invaluable to the steamships on the Great Lakes. At this time the purpose of a ship log was to fix the latitude and longitude of the ship at sea. Until modern technology developed instruments to do this, it was done in clear weather by observing the sun or stars, or by landmarks if the ship was near enough to shore. However bad weather created a serious navigational problem for ships. It caused ships to run slowly, increasing the danger of going onto reefs or rocks or drifting off course.
David Carroll made his Leway ship log with two wheels, lowered down through a pipe in the vessel, reaching about four feet below the bottom of the ship. These wheels were connected to the indicator by wires. The indicator was on deck and had two dials, one for headway and the other for leeway of the drift. The dials had hands that pointed to the distance as clock hands pointed to the time.
After a successful test of his log in 1880, the captain who tested the device was giving a big puff in the Chicago and Buffalo papers, but David had a hard time trying to get the log manufactured. In December 1881, he moved his family to Sheffield, Ohio, in order to work in the lumber business and try to raise more funds to keep his family and his log.
Neither historic nor contemporary logs have David Carroll’s name on them, but his principles are still operating. Every time a Patent log, Chip log, Taffrail log, Forbes log, or Pitometer log is operated by modern mariners, David’s invention gains new momentum.
David Carroll is a holder of several other US and Canadian patents, besides the above-mentioned one for the adding machine: US pat. No. 64628 from 1867 (reissued 1879) for a stump-extractor, US197995, and US303115 from 1884 for a ship’s log, and CA8297A for a nautical log.
David Carroll died on 5 July 1888, in Union City, Erie County, Pennsylvania, and was buried in the local Asbury Cemetery.