Henrici's harmonic analyser

Henrici harmonic analyser (Professor Henrici's original model)

In 1889, the German mathematician Olaus Henrici produced his first harmonic analyser at the mechanics laboratory that he set up at Central Technical College as its founding Professor of Mechanics and Mathematics (one of the constituent colleges of the Imperial College of Science and Technology). The machine was designed to break down a complex wave, such as a sound wave, into its fundamental and harmonic components in order to analyse it and understand its properties. A few years earlier William Thomson (later Lord Kelvin) had produced the first such device in order to analyse tidal curves but his machine was large and difficult to manoeuvre. Henrici's analyser filled the gap for a smaller and transportable machine at a time when applications of harmonic analysis (the mathematical procedure for describing and analyzing phenomena of a periodically recurrent nature such as sound and tidal waves) in engineering and mathematics were growing. Henrici's obituarist, Micaiah Hill, recognised his harmonic analyser to be 'his most original piece of work.'

In 1894 along with Archibald Sharp, his assistant at the Central, Henrici designed a more advanced machine which was manufactured by Coradi in Zurich (an example of this machine is also in the Science Museum collection.) Although it was recognised as a leader in the field, it was rather expensive and so it did not meet the manufacturer's sales expectations. They were mainly bought by universities in Europe, Russia and the United States, as well as the Tokyo Earthquake Investigation Committee.