From the Keuffel and Esser catalogue in 1895:
The Charpentier Calculator is a circular Slide Rule 2 3/8 in. in diameter, with a circular slide which is revolved and set by the handle as may be required. This instrument reads scale against scale like the ordinary slide rule, and being made of metal, is but slightly subject to atmospheric variations. Square roots, sines and tangents as well as logarithms may be found with it, and as the circular sclae is equivalent to a straight one 5 7/8 in. long, results may be read off with a fair degree of accuracy. The small dimensions and light weight of the instrument make it a most useful pocket companion.[^Keuffel & Eser Catalogue, 1895, p. 185, http://mccoys-kecatalogs.com^]
References
- Instruction Notice for Charpentier Calculimètre (in French)
- Bob Otnes, "The Charpentier Calculator", The Journal of the Oughtred Society, Vol 0, No 0, August 1991, pp. 9-11.
- Gonzalo Martin, "Calculimetre de G. Charpentier", Juilet 2009.
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