Hill 60.--Four more attacks occurred in May, notably in the region of
Hill 60. "On May 1st another attempt to recapture Hill 60 was supported
by great volumes of asphyxiating gas which caused nearly all the men along
a front of about 400 yards to be immediately struck down by its fumes."
"A second and more severe gas attack under much more favourable weather
conditions enabled the enemy to recapture this position on May 5th.
The enemy owes his success in this last attack entirely to the use
of asphyxiating gas." "It was only a few days later that the means which
have since proved so effective of counteracting these methods of making
war were put into practice." (Official despatches, 1915.) The despatch
further described how violent bombardments, the confusion and demoralisation
from the first great gas surprise, and subsequent almost daily gas attacks,
prevented the proper reorganisation of the line in question.

Origin of German Gas Shell.--After May a long period elapsed
during which the Germans confined their war chemical activities
on the front to the use of gas shell. Schwarte's book describes
their origin as follows:--"The main idea which influenced
the FIRST construction of a German projectile containing chemicals
(October, 1914) was that of adding to the charge an irritant substance,
which would be pulverised by the explosion of the projectile,
and would overwhelm the enemy with a cloud of dust.
This cloud would hover in the air and have such an effect
upon the mucous membranes that, for the time being,
the enemy would be unable to fight in such an atmosphere.
By altering the construction of the 10.5 c.m. universal
shell for light field howitzers, the `N.i' projectile
was created in the form of 10.5 c.m. shrapnel, the bullets
of which were embedded in a sternutatory powder (double salts
of dianisidine) well stamped down, instead of an explosive.