my Russian companion briefly. "We will stay here until it
is over."

Though we must have been nearly a mile behind the firing-line, the air
was filled with a sweetish, sickish smell which suggested both the
operating-room and the laboratory. So faint and elusive was the odor
that I hesitated to follow the example of the others and don my mask,
until I remembered having been told at Souchez, on the British front,
that a horse had been killed by gas when seven miles behind the lines.

It is a logical development of this use of chemicals as weapons that
the horses in use on the French front are now provided with gas-masks
in precisely the same manner as the soldiers. These masks, which are
kept attached to the harness, ready for instant use, do not cover the
entire face, as do those worn by the men, but only the mouth and
nostrils. In fact they resemble the feeding-bags which cartmen and
cab-drivers put on their horses for the midday meal. Generally
speaking, the masks are provided only for artillery horses and those
employed in hauling ammunition, though it now seems likely that if the
cavalry gets a chance to go into action, masks will be worn by the
troopers and their horses alike. After a large gas attack the fumes
sometimes settle down in the valleys far behind the lines, and hours
may elapse before they are dissipated by the wind. As it not
infrequently happens that one of these gas banks settles over a road
on which it is imperative that the traffic be not interrupted, large
signs are posted notifying all drivers to put the masks on their
horses before entering the danger zone.

There are now three different kinds of gases in general use on the
Western Front. The best known of these is a form of chlorine gas,
which is liberated from cylinders or flasks, to be carried by the wind
over the enemy's lines. Contrary to the popular impression, its use is
not as general as the newspaper accounts have led the public to
believe, for it requires elaborate preparation, can only be employed
over comparatively flat ground, and then only when the wind is of
exactly the right velocity, neither too light nor too strong. Another
form of asphyxiating gas is held in shells in liquid form, usually in
lead containers. Upon the bursting of the shell, which is fired from
an ordinary field-gun, the liquid rapidly evaporates and liberates the
gas, a few inhalations of which are sufficient to cause death. The
third type consists of lachry