The Stanhope Calculator

1775 · Stanhope Mechanism · Work 406 of 1,871

The Stanhope Calculator, 1775, Stanhope Mechanism

A rectangular calculating machine in a case of mahogany and brass, a row of small round numeral windows across the upper brass face, each window showing the single digit 0, sliding setting bars below them in parallel slots with small ivory pointers, a crank on the right side, a brass carrying handle on the lid, every other surface plain brass and figured mahogany, standing on a dark baize-covered table before a deep neutral background, a single raking light from the left raking across the slots of the setting bars.

What it was used for
Charles Stanhope, 3rd Earl Stanhope, signed as Viscount Mahon; the machines were made by James Bullock in London; according to Martyn Downer Stanhope never sought financial reward for any of his inventions. There are three different machines, to be kept apart. Four-function machines of 1775 and 1777 — the Science Museum records the second as "Calculating machine invented by Charles Stanhope in 1777, made by James Bullock", inv. 1872-137, "Known as the Leibniz type". Separate from these, a coplanar toothed-disc adding machine of 1780, twelve-digit and, according to the Arithmeum, set up for English currency "from 'Farthings' to 'Hundred Million'", inscribed "Visc[oun]t Mahon Inv[enit] 1780 Ja[me]s Bullock Fecit"; the original is in the Old Ashmolean at Oxford.
What was new
Here the entry stays thin, and that is the finding. One constructional feature of the 1780 machine is documented: according to the Arithmeum Stanhope avoided intermediate gears, which makes the result displays turn in alternating directions. For the 1777 machine a fully automatic tens carry is claimed; the analysis is Michael Wright's, printed by Martyn Downer, who exhibited the machine in 2008, as his contribution to the exhibition catalogue. The barb is what survives: Downer names three surviving examples, one of them only a fragment, and the Science Museum holds, beside the machine, a "small trial piece". Both pieces reached the museum through H. P. Babbage and, according to Wright, had belonged to Charles Babbage — Stanhope's machines became collection items of the next generation of calculating machines rather than tools of their own.

Further reading