Coradi Harmonic Analyzer No. 61 in Case

In the early nineteenth century, the French mathematical physicist Joseph Fourier showed that many mathematical functions can be represented as the weighted sum of a series of sines and cosines of differing period (e.g. as the sum of harmonic functions with differing coefficients). An apparatus arranged to mechanically derive the Fourier equation of a curve is called a harmonic analyzer. The first account of such an instrument was published in 1876 by the British physicist William Thomson (Lord Kelvin). His device, which occupied considerable space, was used especially for tide prediction. In 1889 the German-born British mathematician and physicist Olaus Henrici developed a new, more compact, form of harmonic analyzer. He showed his model, as improved by Archibald Sharp, to G. Coradi of Zurich, who already was known as a maker of planimeters and integrators. Coradi made further improvements and began manufacture.

This harmonic analyzer has a five glass spheres. It is in a wooden case. To find different terms in the Fourier expansion of a function, one uses different discs in the machine. These are stored in a separate case that has catalog number 323829. Documentation that describes the two Coradi harmonic analyzers in the NMAH collection is stamped “James W. Glover (/) 620 Oxford Rd. (/) Ann Arbor, Michigan." Correspondence received with the object relating to Glover's 1928 attempt to purchase a harmonic analyzer has museum numbers 1987.0705.005 and 1987.0705.06. Hence it seems likely that the harmonic analyzers were purchased for James Waterman Glover (1868-1941), a member of the faculty of the Department of Mathematics at the University of Michigan from 1895 to 1937. Glover offered the first courses in actuarial science taught at the university.

References:

O. Henrici, "On a new Harmonic Analyser," London, Edinburgh & Dublin Philosophical Magazine, 5th Series, #38, July-December 1894, pp. 110-121.

G. Coradi, "Instructions for the use of the Harmonic Analyser Gear Wheel Type."

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