Note: Do not rely on this information. It is very old.
Fourier Series offer a method of analysing any irregular curve and determining simple harmonic constituents that shall, within any assigned limits, combine to produce the curve. This is the geometrical representation of the problem, which has, however, a far-reaching application in the higher branches of physical science. To take one example, the irregular distribution of heat conducted from the surface of the earth to the interior may, by means of the Fourier series principle, be analysed into a number of simple harmonic distributions. [Harmonic]