Clarence Elmer Locke (1865-1945), a civil engineer and businessman from Kensett, Iowa, USA, was a holder of two US patents for a simple calculating device—slide bar adder, which became popular as Locke Adder. The first patent was granted on 24 December 1901 (US pat. No. 689680), the second (No. 779088) in January, 1905. The Locke Adder was quite similar to the earlier Universal Adding Machine of George Fowler.
The eye-catching Locke Adder (see the nearby photo), with elaborate Victorian scrollwork stamped into aluminum sheet metal painted black or copper/bronze, is a row adder, made by metal (stamped tin and aluminum), paper and cloth, with measurements: 2 cm x 29.5 cm x 12.3 cm. It used alternating fixed and moveable horizontal bars of hollow aluminum, as carrying from one column to another is manual.
The nine moveable slides show either red or green while in the zero position, and expose either silver or yellow as the slides are moved to the right. Between the slides are eight fixed bars, painted black with white numbers from 1 to 9. The sliding bars of hollow aluminum are manipulated with the fingers in order to determine sums.
A number is entered on a given bar by placing the index finger on the raised knob corresponding to the desired digit and sliding the knob leftward as far as possible. The user must account for a tens carry manually by a combination of a rightward adjustment of the current bar and the advancement of the bar above by one, much as is done with a traditional abacus. The split-colored sliders aid the user in recognizing and carrying out the tens carry operation.
The Locke Adder was a very beautiful, but not a user-friendly calculator. As usual in those days, it was touted as a four function machine, although multiplication and division require you to do much of the intermediate action in your head, then add or subtract the partial results on the adder. The Locke Adder enjoyed a modest (albeit brief) success, thanks to its low price and an extensive print advertising campaign in the first few years of the 20th century (see the nearby image). It was on the market for less than ten years, probably being supplanted by dial adders such as the Calcumeter of Walsh and Morse.
The machine was manufactured by the inventor himself in his company—C. E. Locke Manufacturing Co., 98 Walnut str., Kensett, Iowa. The prices were: 1901-05: price $5; 1906/; price $5 (oxidized copper finish) and $10 (oxidized silver finish with case); 1908: price $5 & $10. It was exposed with success at the St. Louis World’s Fair of 1904 (alongside an other calculating device, made by company—an adjustable calculating table). If you believe the advertising, these devices were so useful and perfect that they should have made the invention of the computer superfluous:
Why don’t you use the Locke Adder? It’s the modern office appliance that is practically adapted to the needs of a growing business. The Locke Adder takes care of the computation of business details. No office systematically equipped without it. It’s the fastest, simplest, handiest, most practical, durable, low priced calculating machine. Adds, Subtracts, Multiplies, Divides. Easily learned-lasts a lifetime. It’s more rapid than you and always accurate. Quickly pays for itself. Ensures accuracy, releases from mental strain. Adds all columns simultaneously. Capacity 999,999,999. It is a valuable aid to the busy accountant, and as this useful machine, can be had for only $5.00, one should be in every business office.
Biography of Clarence Locke
Clarence Elmer Locke was born on 15 November 1865 in Milton, Wisconsin, as the firstborn in the family of Charles Locke (1836-1903), a Civil War veteran from New York, and Mary Elmer (Holden) Locke (1841-1908) from Vermont. They married in December 1864 and besides Clarence Elmer, they had one more son, Wilbert F. (1879-1958), and a daughter, Jessie Mabel (1874-1967), and two children who died in infancy. Charles Locke was a farmer in Milton, Wisconsin, until early 1870s, when he moved with his family to Kensett, Iowa, where he became a prosperous lumberyard owner and merchant.
Clarence Elmer graduated from Cornell College in Mt. Vernon, Iowa, in 1892, as Bachelor of Civil Engineering and in the next year he married to Fannie Webb (1867-1964), from DeWitt, Clinton County, Iowa. The family had five children, but only two of them survived to adulthood: Lowell F. (1894–1978), who became a soil scientist and worked for US Government, and Dorothy H. (born 1904).
In the middle 1890s Clarence worked for a time as a civil engineer in Minnesota, but eventually joined his father’s lumberyard business in Kensett, Iowa, where he worked as a dealer of lumber and coal. In early 1900s he founded C. E. Locke Manufacturing Co., of Kensett, Iowa, to manufacture his patented adding device. Besides the above-mentioned patents for an adder, Locke was a holder also of another patent for a hand stamp (US pat. No. 686815 from 1901).
Around 1910 Clarence Locke left his adding machine manufacturing and merchant businesses and moved with his family to Dona Ana County, New Mexico, where he bought a farm and took up farming.
Clarence Elmer Locke died on 15 July 1945, in Mesilla, Dona Ana, New Mexico.