Leonhard Euler. Engraving of Leonhard Euler (1707- 1783), Swiss mathematician, being rescued from a fire in 1771. Euler's house was burned down during the great fire of St Petersburg, Russia, and had to be carried to safety by his Swiss servant, Peter Grimm. Euler was a professor at St Petersburg Academy at the time. Although he had become blind in 1766, Euler had a remarkable memory and was still a prolific mathematician. During his life, Euler developed the theory of differential equations, the calculus of variations, and did important work in astronomy and optics. He published 800 papers, contributing to all areas of pure and applied mathematics.