Air-cock. Is the same as a pet-cock and is used to relieve pipes that are air-bound.
Air Cock.
Annular Valve. From annular—a ring—i.e., a round valve with a hole in the middle.
Area. The extent of surface, as the area of a piston.
Assembling. Putting together the parts of a machine.
Atmospheric Pressure. The pressure of atmospheric air, not only downward but in every direction, this amounts to about 14.7 lbs. per square inch at the sea level. Usually taken at 15 lbs. to facilitate calculations.
Auxiliary. Something to “help out,” as an auxiliary cylinder or an auxiliary piston.
Ball Check-valve. One in which a metal ball is used in place of a poppet-valve.