ABSTRACT
Hamilton’s principle of mechanics corresponds to Fermat’s principle of optics. In fact, this is not quite true. The correct variational principle of mechanics with which Fermat’s principle can be related, is Maupertuis’ principle, or the principle of least action. Euler equations are also the same as those found in optics. Maupertuis’ principle is, therefore, the equivalent in mechanics of Fermat’s principle of optics. There is a relation between the conservation of angular momentum in mechanics, and the skew invariant in optics.
