Adolphus Dennis

Adolphus Sylvester Dennis (1857-1942), a former teacher at the Commercial College in Iowa City was an inveterate typewriter, calculator, and adding machine inventor, a man to whom at least 23 USA (as well as several Canadian and Great Britain) patents were issued, 12 of which were for typewriters. He also designed calculating machines, adding and recording machines, a “typographical adding machine” and a “computing machine”.

The patent drawing of Dennis Typographical Adding Machine, US pat. No. 657266
The patent drawing of Dennis Typographical Adding Machine, US pat. No. 657266

At the end of the 1880s, Dennis designed, and in 1890 patented, a typewriter with advanced duplex construction. In the early 1890s, he tried to attract business investors for its production and succeded. Dennis Duplex Typewriter Company of Des Moines, Iowa, started production in 1893. Despite predictions, the machine never took off and was manufactured for only a short time.

After this failure, around 1895 Dennis moved to Cleveland, Ohio, and started to design calculating and typewriting machines for the local manufacturers. The first patent of Dennis for a calculating device was US657266 (see the patent, applied 7 Dec 1895) for a typographical adding machine.

The typographical adding machine of Dennis employed one adding wheel and many totalizing wheels mounted in a sliding carriage and adapted to be engaged successively and operated by the adding wheel. His object was: (1) To provide an adding machine of simple, cheap, strong, and durable construction. (2) To provide in machines of this class having a series of totalizing wheels improved means for carrying the tens to the adjoining wheel to the left, for returning all of the wheels simultaneously to zero, and for elevating the wheels out of contact with the adding-wheels, so that printing may be carried on without the adding. (3) To provide improved and simplified paper and ribbon advancing mechanism to be operated by a return of the carriage.

Biography of Adolphus Dennis

The Dennis Duplex Typewriter from 1890s
The Dennis Duplex Typewriter from the 1890s

Adolphus Sylvester Dennis was born on 12 May 1857 in Williamsburg, Clermont, Ohio. He was the son of William M. Dennis (1821–1907) and Eleanor (Foster) Dennis (1821–1880), who married in January 1842 and had nine children—3 girls and 6 boys (Adolphus was the 4th son). In the middle 1860s, the family moved west to Iowa, where William used to work as a farmer. Adolphus spent his youth in Des Moines, Iowa, where on 24 June 1885 he married Francisca R. Cummings (1855-1920). They were the parents of at least one son and a daughter: Arthur Cummings (29 Jan 1887–3 Dec 1918), and Martha Sarah (1889–1982).

At the end of the 1880s, Dennis developed an advanced duplex typewriter. The design of this novel machine incorporated the use of two sets of keyboards, allowing users to push two keys at the same time, greatly increasing the speed at which a worker could produce documents. Some business people predicted the amazing new machine would replace the use of shorthand in offices. The Dennis Duplex Typewriter was showcased at the 1893 World’s Fair in Chicago. It received rave reviews for its performance, style, and durability. A fair committee highlighted the machine’s features: it doubled the speed of other typing machines, it could print two different letters of the alphabet as quickly as one letter by the traditional machines, it had two points of contact between the keys and paper, and it was strongly built. Although it was described as a “peculiar” invention, fairgoers also called it “ingenious.”

Business machine dealers who witnessed the Dennis typewriter in action at the fair proclaimed it the “finest automatic machinery in the world.” Their endorsements helped Dennis as he looked for additional investors for his factory back in Des Moines. He had plans to employ up to a thousand men within ten years at the factory where his machines would be built. The Humeston New Era newspaper reported that the typewriter’s World’s Fair exhibition allowed operators from all over the world to see the machine, and they were highly impressed. The article reported the machine—the “fastest writing machine in the world”—would become world famous. In fact, dealers from South Africa, South America, New Zealand, and Russia were applying to handle the duplex typewriter in their countries. In America, nine large cities now had dealers in the new typewriter.

George Anson Jewett (1847-1934)
George Anson Jewett (1847-1934)

Dennis wined and dined business investors in Des Moines. At one event he gave a lunch for prospective investors. About 150 people showed up to hear about the machine. Dennis said he had already invested $100,000 in his project. He asked attendees to help promote the machine as a “distinctively Des Moines invention.” An expert typewriter showed off the features of the machine at lunch, writing a sentence at the rate of 190 words per minute. He claimed he had been using one for a year and at one time had written as many as 206 words a minute on the duplex. It was reported that orders were already coming in for the machine.

George Anson Jewett (1847-1934), a Des Moines businessman, went into business with Dennis, and together they manufactured the duplex machine. Despite predictions, the machine never took off. It was over-produced and unnecessarily complicated, so it did not do well and its unique keyboard layout was scrapped.

After the failure of Dennis Duplex Typewriter, around 1895 Adolphus Dennis moved with his family to Cleveland, Ohio, where he continued his inventions. In the late 1910s, he moved to Oakland, California, and was still designing machines up to the early 1940s. For his last patents, Dennis applied on 30 Dec 1941, for a power-driven typewriter (US pat. No. 2331827), and for a calculating machine (US pat. No. 2365527), both assigned to Friden Calculating Machine Company. His son Arthur Cummings Dennis became a geologist and went into petroleum geology, working for various companies in the Midcontinent, but died young (together with his wife Alma Louise Proffer) with Spanish influenza in Wyoming in Dec 1918. Their thirteen-month-old daughter Frances managed to survive and was taken back to Oakland, California to be raised by her grandparents, Mr. and Mrs. Adolphus Dennis.

Adolphus Sylvester Dennis died on 23 May 1942 in Alameda County, California.