bravais taught a course in applied mathematics for astronomy in the faculty of sciences in lyon, starting in 1840. he succeeded victor le chevalier in the chair of physics at the ecole polytechnique between 1845 and 1856, after which he was replaced by henri hureau de sénarmont. in 1846 he published a paper on the statistical concept of correlation, and arrived at a definition of the correlation coefficient before karl pearson. he is, however, best remembered for his work on bravais lattices, particularly his 1848 discovery that there are 14 unique lattices in three-dimensional crystalline systems, correcting the previous scheme, with 15 lattices, conceived by frankenheim three years before.