A law of physics that says that a confined fluid transfers the externally applied Pressure evenly in all directions. Blaise Pascal, by using the columns mercury-barometer of Evangelista Torricelli demonstrated the decrease in atmospheric pressure with increasing altitude and determined that atmospheric force at a point equal to the pressure exerted in all directions. More accurate in a static fluid, the strength of the speed of sound in the fluid. Force acts normal to any surface. This natural phenomenon is the basis of the pneumatic tires, balloon, hydraulic jack, and related devices.