The William Hart’s story had many twists and turns. He was a watchmaker, jeweler, businessman and prolific inventor. Hart had quite a few patents for various instruments and devices, but it seems these devices were never used. That’s not the case however with his calculator, known as Hart’s Mercantile Computing Machine, US patent No. 199289 from 15 January 1878 (the witnesses of Hart’s patent were Abraham Slingerland, a wealthy Kirksville lawyer, and Albert Dutcher, his partner in jewelry business).
The device was patented as a Calculator and Improvement in Mechanical Accountants, but was sold under the name Hart’s Mercantile Computing Machine (see the nearby photo). There are several of these calculators known to exist now. One of Hart’s calculators is on display in the Smithsonian National Museum of American History (see the image below). According to a local newspaper, Kirksville Missouri Democrat for 16 July 1888, by then Hart had sold 3500 of these devices and he lately ordered one thousand more. Smithsonian’s calculator indicate Scovill Manufacturing of Waterbury, Connecticut, and a company by the name of J. W. Strange, Bangor, Maine, made it. Scovill was a maker of brass products, Strange was an instrument maker.
The calculator of Hart is similar to the earlier devices of his compatriots Amos Mendenhall, Alonzo Johnson, and Elmore Taylor. It is housed in a cylindrical wooden case (with cover), with diameter 13.5 cm and height is 5.5 cm, its weight is 155 g. The instrument itself is made by steel and brass, and has a wooden handle.
The calculating device of Hart consists of three concentric brass discs, a brass marker, a steel stop, and a long wooden handle with a pointer coming down from its end, which rotates the upper disc over the lower one to add numbers up to 99. Each brass disc has the numbers from 0 to 99 stamped around the edge. The two inner discs both have a circle of 100 holes just outside the numbers. The inner holes are used to add the last two digits of a number by rotation. Any hundreds value in the sum carries to the second set of holes, which are used to add hundreds and thousands places. When the total exceeds 99, a hand like the short hand of a watch automatically advances one to indicate the hundreds value (the adder has a single carry). Sums of up to 9999 can be indicated.
Biography of William Hart
William Henry Hart was born on 15 July 1828, in Lodi, a village in Seneca County, New York, United States. Until the Civil War Hart and his family lived in Dodge County, Wisconsin (Leroy, Williamstown, and Mayville). In 1867 Hart family moved to Kirksville, Missouri, where Hart became one of its prominent and most trusted business men, and opened a jewelry store in the square, doing business as W. Hart Jeweler. In 1874 Hart ran for City Council but lost. In 1875 he entered a partnership with Albert Dutcher, a local jeweler, and then sold his share of the firm to Dutcher. Because of declining health, Hart said that he wanted to take up something giving more outdoor exercise.
In 1850 William Hart married to Elizabeth Davidson (1831-1894) from Pennsylvania. They had eight children: Emma Delilah (1851-1928), Rosalie (1853-1942), Henry (1855-1930), Sarah Sadie (1861-1924), twins Lawrence and Clarence (b. 1866), Volney (1872-1890) and Waren (1873-1877).
The 1880 Federal Census shows Hart’s occupation as a watchmaker. In 1886 Hart went back to jewelry business in the firm of Hart & Miller, and then as a owner of Hart’s Jewelry Store. In December, 1890, in a fire, which destroyed the store of Hart, his son Volney died, William Hart barely survived with a broken right leg and burns on the hands and face. By 1892, Hart was back in the jewelry business again, known now as Hart & Son, with his son Lawrence who later became an osteopath.
William Hart obviously was a very good mechanic and prolific inventor, because he had at least 13 patents for various instruments and devices, let’s mention only: second-hand holder and screw-end finisher (US patent 264532), graphophone-reproducers (US665601, US648406, US644981, US651308 and US817062), clock-escapements (US33990, US326292 and US106815), hammer for posting bills and cards (US217101), ruby-pin and pallet setter (US264533).
In 1884, William Hart (together with his wife) was one of the incorporators of the Spiritual and Liberal Association, which believed that certain spirits of a deceased manifested themselves and, in some instances, conversed with their friends on earth.
After the death of his wife on 27 January 1894, Hart continued his work and inventing, but eventually he leaved Kirksville and USA, and relocated to Mexico, where two of his children (Henry and Rose) lived. Hart remained in Los Mochis, Sinaloa, Mexico (a town, founded by a group of American utopian socialists), until his death on 2 April 1907.