This instrument draws the integral of a function that is plotted when the curve representing the function is traced with the tracer. The instrument rests on two German silver rollers attached to a common axle. A framework above the axle carries the tracer arm, the integrating mechanism, and the plotter. A pen point, a pencil point, a calibration bar, a screwdriver, and a knob for the pencil point are stored separately in the case. Discussion of instruments used to draw the integral curve of functions dates from the 1830s. In 1878 the engineer Abdank-Abakanowitz introduced the instrument that would be considerably modified and sold by Coradi from about 1890. The integraphs sold by Coradi before about 1903 had a much larger framework surrounding the axle. Although this object was sold by Keuffel & Esser, no model #4295 integraph is listed in K&E catalogs for 1906 through 1944. The device was sold after K&E opened its San Francisco office in 1901, as this office is mentioned on the paper sticker in the lid that gives the model and serial number. The card in the lid of the box indicates that the instrument was purchased from Roebling, who built the Brooklyn Bridge, in 1940. The card has been corrected in pencil to indicate that the vendor was in fact Roebling's son. Neither John Augustus Roebling (1806-1869) nor his son Washington A. Roebling (1837-1926), both of whom worked on the Brooklyn Bridge, was alive in 1940. John A. Roebling II, W.A. Roebling's son, lived from 1867 to 1952. It seems likely that he or possibly a cousin sold the instrument.
Keuffel & Esser Co., Keuffel & Esser Co. its Origin, Growth and Present Scope, New York & Hoboken (1909).
Maurice d'Ocagne, Le Calcul Simplifie (1928).
Horsburgh, ed., Handbook of the Napier Tercentenary Celebration (1914) .
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