Victorian illustration to download showing a pile driver powered by atmospheric pressure during the construction of a coffer dam in London docks, 1848. This machine was invented by the engineers Thomas Clarke and John Varley. A steam engine and air pump are connected to the air cylinder by a pipe (left). The air cylinder has a piston inside, connected to a pulley and the rammer. The variation of atmospheric pressure in the cylinder causes the piston, and thus the rammer, to rise and fall. The advantage of this machine was that it was easy to move and re-assemble, unlike machines where the bulky steam engine was an integral part of the machine.