Boiler

(boil'r,) a ve el in which water is boiled for the purpose of raising steam for the machinery of a factory; or a closed vase of wrought iron, or copper, in which water is vaporized, and employed in the gaseous form, to impre movement upon steam-engines or other machines. In this case, the effect of the machine is dependent upon the conversion of the water into vapor, and this power is the only one used. The boiler must then satisfy certain conditions which are of the highest interest. Thus, as the motive power of the engine depends upon the exce of the pre ure of the steam in the boiler, it is nece ary that the latter should be of sufficient strength to resist it; and as the heat applied is always more or le costly, it is important that the fireplace should be constructed so as to employ the whole of it. [s. 101]