which were non-persistent and were expected to penetrate the mask.
So strong was this tactical conception that the Allies were on
the verge of adopting a uniform shell marking based on this
principle throughout their armies.

Special Gas Weapons and Appliances.--It is a popular misconception
that gas was only discharged from cylinders in huge clouds,
or used as artillery shell. A number of special weapons developed,
which were particularly adapted for gas. Thus, the Livens projector,
which was a great Allied advance, produced a gas cloud a long distance
from the point of discharge, while the Stokes and other short range
guns were used for rapid fire of large numbers of gas shell.

The primary conceptions with regard to protection have been brought
home to so many, through the fact that the mask was a part of the
equipment of every soldier, that we need not dwell on them here.
It is not generally realised, however, that every modification
introduced by either side was a vital and direct counter to some enemy
move planned to render the protection of the opponent ineffective.

Gas Shell.--A word is necessary to define the use of gas shell.
The point which must be realised is that gas, and in
particular gas shell, fulfilled a special purpose in warfare,
from which it was much more suitable than explosives.
The use for neutralising batteries, cross roads, and rendering
whole areas uninhabitable, is developed fully in our reference
to the great German attacks in 1918.

With this brief sketch to clear the ground, we can embark more freely
upon the account of chemical warfare which follows. CHAPTER II