Kelvin's harmonic analyser, 1878.
© Science Museum / Science & Society Picture Library
Invented by William Thomson, Baron Kelvin of Largs, (1824-1907), pioneering Irish physicist. The harmonic analyser was designed to analyse graphical records of daily changes in atmospheric temperature and presure. It was brought into use by the Meteorological Office in 1878. The tracing point is taken along the curve to be analysed, and its movement causes the seven discs to rotate. Rolling spheres communicate this motion to the recording rollers.