The Ypres Times.
149
a truck load or more of cylinders as near the front line as possible and then releasing the
gas instantaneously when the wind conditions were favourable. This gave a very con
centrated cloud with a long effective travel. The German cloud gas attacks were improved
in efficiency towards the end of 1915 by the addition to the chlorine of increasing
quantities of phosgene, which is a much more dangerous lethal gas. Fortunately for us,
the necessary protection had been secured in time, and this fact, coupled with the pre
vailing westerly winds, rendered cloud gas somewhat ineffective from the German point
of view and its use was abandoned. The last cloud attack on the British front was on
August 15th, 1916.
As a natural sequence, the development of gas shells was taken up, as gas is a more
flexible weapon when used in projectiles not only is its use to a great extent independent
of the wind direction, but a much greater variety of toxic substances can be employed in
shell than in cylinders. The French were the first to see the possibilities of an all gas
projectile, their phosgene shell being very effective in the defence of Verdun in the spring
of 1916. The Germans at once took up the idea and used gas shell of the lethal type,
mainly Green Cross, with small bursting charges in place of the previous heavy bursters.
Owing, however, to their exaggerated notion of the toxic value of the fillings, they
scattered their shell over wide areas instead of concentrating them in surprise bursts on
important points consequently, we suffered only slight losses except during the first
period of surprise. Our gas shell supplies were comparatively poor in 1916.
In 1917, the development of gas projectiles proceeded actively both in Germany and
in Great Britain and France, and they became a serious factor in the tactical situation,
which had constantly to be borne in mind. Though our gas production was restricted
and impeded by the lack of a highly organised and developed chemical industry, such as
Germany possessed, nevertheless we were able in 1917 to employ considerable quantities
of lachrymatory and lethal shells, the fillings being S.K. (a lachrvmator)C.G. (or phosgene)
and N.C., of which the active constituent is chloropicrin. According to prisoners' state
ments and captured enemy documents, we achieved considerable material results with
our shell.
In 1917, the development of gas projectiles proceeded along two independent lines.
First came their use to reduce the efficiency of troops by compelling them to wear
respirators the reduction in efficiency depended, of course, on the state of gas training,
the type of respirator, and local conditions. For this purpose, shell with persistent fillings,
i.e. liquids which vaporise slowly and give off poisonous or irritant vapours for a long
time, were obviously the most economicallachrymators were then typical examples of
such fillings. The second idea was to produce casualties, and for this purpose it is necessary
to use a gas which is not easily detected, or to produce a surprise concentration sufficient
to injure a man in the few seconds that elapse before his respirator is adjusted. With
the latter end in view, we developed the Livens' projector, which the Germans did us the
honour of copying. This projector was a very crude form of trench mortar, very inaccurate
in range and direction the bomb held 30 lb. of phosgene, and its filled weight was 60 lb.
To compensate for their inaccuracy, the projectors were fired simultaneously in large
numbers on to specially selected targets so that a very high concentration of gas was
instantaneously' produced on the target, so high that not only was anyone not wearing the
respirator killed at once but even respirators were penetrated.
In the early part of 1917, the Germans were still using their Green Cross shell, but
thanks to the efficacy of the British box respirator and to their own mistaken gas shell
tactics, the efforts were poor. They had, however, been busy in looking for alternatives,
and they sprang two new gases upon the Allies in July, 1917. The first, which was
without doubt the most effective battle gas, was introduced in their Yellow Cross shell.
Its chemical name is dichlorodiethyl sulphide, but it has come to be known as mustard
gas on account of its smell and blistering properties, or as Yperite, the name given to it
B
