The mystery shall be vested in a cell, without air and moisture--The barometer--The column barometer--The wheel barometer--A very simple barometer--The aneroid barometer--Barometers and weather--The diving-bell--The diving-dress--Air-pumps--Pneumatic tyres--The air-gun--The self-closing door-stop--The action of minute projectiles; they pirouette and spin so quickly round, that the.