Torricelli was the first scientist to point out that wind is
caused by differences of atmospheric pressure.
Pascal’s law applies to liquids and gases. Pressure on
a fluid at any point is transmitted undiminished throughout the
fluid to all constraining points. Equal areas experience equal
pressure, so that the pressure transmitted to an area is
proportional to the size of the area.
Otto von Guericke invented the first vacuum pump and
conducted his famous Magdeburg hemispheres experiment to
demonstrate the force of atmospheric pressure.
See also in The book of science:
Readings on wikipedia: