In 1738, a Swiss physicist and mathematician named Daniel Bernoulli (1700–1782) discovered that when the speed of a moving fluid increases, such as the wind blowing through the corridors of a city, the pressure of that fluid decreases. Bernoulli discovered this while measuring the pressure of water as it flowed through pipes of different diameters. He found that the speed of the water increased as the diameter of the tube decreased (the continuity principle), and that the pressure exerted by the water on the walls of the pipes was less as well. This discovery would prove to be one of the most important discoveries in fluid mechanics.