1851 move from Königsberg to Paris and joining of the workshop of the violinmaker Jean Baptiste Vuillaume; seven years of working with Vuillaume; master violinmaker; attendance of public lectures and studies of mechnics during his leisure time; 1858 own business as an acoustical instrument maker for scientists; 1859 first catalogue issued; active research on his own; 1858 psychological experiments with high pitched tuning forks; about 1863 move into a new instrument shop near the faculty of medicine; 1865 second catalogue published (including several innovations from the theories and instruments of Helmholtz); 1862 invention of the manometric flame capsule; 1866 collaboration with the experimentalist Victor Regnault; 1868 honorary doctorate from the University of Königsberg and beginning of experiments on vowels; 1870 move to Switzerland and Prussia; 1871 return to Paris; 1872 account of his manometric flame studies published; 1875 major experimental critique of Helmholtz's theory of beats and combination tones; 1873 new catalogue published; 1882 collection of all of his writings since 1858 published in book-form; also 1882 new catalogue published, travel to America and series of public lectures given in Toronto; 1889 last catalogue finished; 1899 publication on the production of high frequencies.