Signedon frame of the rightmost roller: G. Coradi Zurich
Inscribedon the frame of the rightmost roller: No. 114
in red crayon inside the lid: Property of Div. / of Mathematics / Written by M. Morse 1929
FunctionThis is a Model 4298 Coradi Integraph. Integraphs are mechanical, analog, computing devices used to plot the integral of a graphically defined function. Their close predecessors, mechanical integrators, require the user to construct curves by calculating point by point. Bypassing this tedious process, the Integraph draws the curves directly on paper on its own making its operation automatic, graphical integration. The Integraph was of particular use to mechanical engineers, naval architects, and physicists. It was used to calculate, among other things, centers of gravity and curves of stability.
In order to operate the Integraph, the user traces a figure (the differential curve) and, with the attached writing implement, the device automatically draws the integral curve. The pointed stylus extension of the device is used to trace. A pen or pencil can be fit into the brass holder extended from the base of the larger silver bar then draws the integral curve on a piece of paper or other surface underneath the device. The tracing motion is mediated through the interceding bars such that the pencil will draw precisely the integral curve of the traced function. For example, if the user traces a graphical representation of the curve sin(x), the Integraph will draw -cos(x). The machine is especially helpful when users are taking multiple integrals. Once the first curve has been traced and the integral curve drawn, the user can then trace the mechanically produced curve, and so forth.
The original catalogue in which the first Model 4298 Coradi Integraph was introduced has been digitized and can be accessed by clicking here. The catalogue describes the materials, specifications, capabilities, and design of the Coradi Integraph Model 4298 and compares its abilities with its immediate predecessor, the Model 4296 Integraph.
A variation of the Model 4298 closer to this one is introduced in the Keuffel & Esser Co. Catalogue in 1936 which can be seen here.
Primary SourcesKeuffel & Esser Co., "Coradi's Mechanical Integraph", in K&E Slide Rule & Planimeter Catalog, (1921), p. 263.
Keuffer & Esser Co., "Coradi's Mechanical Integraph", in K&E Slide Rule & Planimeter Catalog, (1936), p. 348.
ProvenanceFrom the Mathematics Department, Harvard University, December 14, 1984.