Being a liquid, and
possessing as such no definite shape or form of its own irrespective of
the vessel in which it is held, water is by far the more convenient of
the two substances to move about or to deliver in predetermined volume to
the decomposing chamber. A supply of water can be started instantaneously
or cut oil as promptly by the movement of a cock or valve of the usual
description; or it may be allowed to run down a depending pipe in
obedience to the law of gravitation, and stopped from running down such a
pipe by opposing to its passage a gas pressure superior to that
gravitational force. In any one of several obvious ways the supply of
water to a mass of carbide may be controlled with absolute certainty, and
therefore it should apparently follow that the make of acetylene should
be under perfect control by controlling the water current. On the other
hand, unless made up into balls or cartridges of some symmetrical form,
calcium carbide exists in angular masses of highly irregular shape and
size. Its lumps alter in shape and size directly liquid water or moisture
reaches them; a loose more or loss gritty powder, or a damp cohesive mud,
being produced which is well calculated to choke any narrow aperture or
to jam any moving valve.
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