157) By compounding the expansion of steam in two or more cylinders, the ratio of expansion

158) The water tubes in a simple vertical boiler are

159) The ratio of heat actually used in producing the steam to the heat liberated in the furnace, is known as

160) In a La-mont boiler, there is a __________ circulation of water and steam.

161) The diameter of internal flue tubes of a Lancashire boiler is about __________ that of its shell.