Johann Bernoulli (1667-1748) was a Swiss mathematician. He is known for his contributions to infinitesimal calculus (concerned with finding slope of curves, areas under curves, minima and maxima, and other geometric and analytic problems) and educated Leonhard Euler in his youth. He solved the problem of the catenary. In physics and geometry, the catenary is the curve that an idealized hanging cable or chain with very short links assumes under its own weight when supported only at its ends. Mathematically, the catenary curve is the graph of the hyperbolic cosine function. Catenaries appear in architecture and engineering, in the design of bridges and arches. He proposed a fluid energy perpetual motion machine and published a work on hydrodynamics.