of acetylene ever being able to prepare his own carbide, all descriptions
of this latter substance, all methods of winning it, and all its
properties except those which concern the acetylene-generator builder or
the gas consumer have been omitted from the present book. Hitherto
calcium carbide has found but few applications beyond that of evolving
acetylene on treatment with water or some aqueous liquid, hygroscopic
solid, or salt containing water of crystallisation; but it has
possibilities of further employment, should its price become suitable,
and a few words will be devoted to this branch of the subject in Chapter
XII. Setting these minor uses aside, calcium carbide has no intrinsic
value except as a producer of acetylene, and therefore all its
characteristics which interest the consumer of acetylene are developed
incidentally throughout this volume as the necessity for dealing with
them arises.

It is desirable, however, now to discuss one point connected with solid
carbide about which some misconception prevails. Calcium carbide is a
body which evolves an inflammable, or on occasion an explosive, gas when
treated with water; and therefore its presence in a building has been
said to cause a sensible increase in the fire risk because attempts to
extinguish a fire in the ordinary manner with water may cause evolution
of acetylene which should determine a further production of flame and
heat. In the absence of water, calcium carbide is absolutely inert as
regards fire; and on several occasions drums of it have been recovered
uninjured from the basement of a house which has been totally destroyed
by fire. With the exception of small 1-lb. tins of carbide, used only by
cyclists, &c., the material is always put into drums of stout sheet-iron
with riveted or folded seams. Provided the original lid has not been
removed, the drums are air- and water-tight, so that the fireman's hose
may be directed upon them with impunity. When a drum has once been