Jean-Daniel Colladon

Jean-Daniel Colladon (1802 to 1893) was a Swiss physicist from Geneva who is remembered for experiments on sound, light and liquids. He trained first in law, then worked in the laboratories of Ampere and Fourier in Paris. With his friend, the mathematician Charles Sturm, he shared a prize of the Academie des Sciences for measuring the speed of sound and for work on the breaking up of water jets, and later won the Academy's Grand Prize for research on the compressibility of liquids. In 1841 he showed on Lake Geneva that sound travels more than four times as fast in water as in air, sending signals about 50 kilometres between Nyon and Montreux. His demonstration of light carried inside a curved jet of water, reported in the Comptes rendus in 1842, helped establish the principle of total internal reflection that later underlies optical fibre. He also worked on hydraulics, steam engines and air compressors, devised a floating hydraulic generator, and championed the gas lighting that first lit Geneva in 1844.