Examination of the German lachrymatory shells showed that the liquid was contained inside the shell in a sealed lead vessel so that the material should not come in contact with the steel of the shell, which it destroys gradually. Shell of this kind, though termed gas shell, are not really such, as the liquid has to be broken up into fine droplets by the explosive charge of the shell before the vapour can produce its effect. The liquid has no pressure of its own inside the shell and depends entirely on the bursting charge to get it distributed into the atmosphere. The xylyl bromide used by the Germans was not pure, but contained a big proportion of benzyl bromide, showing that it had been made by the action of bromide on coal-tar light oil from which most of the toluene had been removed for the manufacture of the well-known high explosive, trinitrotoluene. The effect of xylyl bromide on an unprotected man is instantaneous and remarkable. Even such small proportions as one volume of vapour diluted with one million volumes of air will at once make a man weep so copiously that he cannot possible keep his eyes open. Obviously a material of this kind has great military value, for though it does not put men out of action permanently by killing them it neutralises their effectiveness to such an extent that for the time being they may be regarded as of no military importance. In strong concentrations the effect on the eyes is most powerful. I have walked into an area which was being bombarded with lachrymatory shells and suddenly got the effect just as if I had been hit in the face. Fortunately the lachrymation has no lasting effect on the eyes, and a man on getting into pure air very quickly recovers. Throughout the spring and summer of 1915 these lachrymatory shells were used in considerable numbers, especially in the vicinity of Ypres, and at times the ramparts of that much bombarded town reeked of lachrymatory vapour and nobody could stay in certain spots for any length of time without having his eyes protected by specially constructed goggles or by wearing a gas helmet right over his head.