The law of heat conduction is also called Fourier law, and the formula is φ =-λ a (dt/dx) and q =-λ (dt/dx).

Fourier's scientific achievements mainly lie in his research on heat conduction and the mathematical methods he introduced to promote this research. Fourier used sine curve to describe the temperature distribution in the paper, and put forward a controversial conclusion: any continuous periodic signal can be composed of a set of suitable sine curves.