Jean Baptiste Joseph Fourier (1768-1830), French mathematician. Fourier devised the Fourier series and the Fourier Integral Theorem. He had a mixed education and for a time studied at military school. After a visit to Egypt as Napoleon's scientific advisor, he returned to his studies. In attempting to show how heat was transferred between two points, he developed his theory of harmonic analysis. This showed that any periodic oscillation could be described as the sum of simple, regular wave motions and thus be expressed as a mathematical series. Fourier's method is now used in the analysis of all wave forms. He was made a Baron by Napoleon in 1808.