complete control over any such sudden strains as result from fog or
other unexpected demands on the gas-producing power of his works;
while a still more important point is that it does away with the
necessity of keeping an enormous bulk of gas ready to meet any such
emergency, and so renders unnecessary the enormous gasholders, which
add so much to the expense of a works, and take up so much room.

Perhaps the greatest objection to water gas in the public mind is the
dread of its poisonous properties, due to the carbon monoxide which it
contains; but if we come to consider the evidence before us on the
increase of accidents due to this cause, we are struck by the poor
case which the opponents of water gas are able to make out. No one can
for a moment doubt the fact that carbon monoxide is one of the
deadliest of poisons. It acts by diffusing through the air cells of
the lungs, and forming, with the coloring matter of the blood
corpuscles, a definite compound, which prevents them carrying on their
normal function of taking up oxygen and distributing it throughout the
body, to carry on that marvelous process of slow combustion which not
only gives warmth to the body, but also removes the waste tissue used
up by every action, be it voluntary or involuntary, and by hindering
this, it at once stops life.

All researches on this subject point to the fact that something under
one per cent. only of carbon monoxide in air renders it fatal to
animal life, and this at first seems an insuperable objection to the
use of water gas, and has, indeed, influenced the authorities in
several towns, notably Paris, to forbid its introduction for domestic
consumption. Let us, however, carefully examine the subject, and see,
by the aid of actual figures, what the risk amounts to compared with
the risks of ordinary coal gas.