Take it altogether, Yellow Cross gas is very much more than an annoyance, but there is no question that good discipline and thorough appreciation and carrying out of the orders laid down for the protection of troops have reduced the losses in very much the same way that the screwed-up discipline reduced the losses after the first introduction of Green Cross Shell. One of the most objectionable features of the mustard gas is the continual care that has to be exercised to prevent casualties. It is so easy for a man whose clothing is slightly contaminated with gas to enter a dugout and contaminate the whole of the interior and all its occupants. Sentries also have to be posted to warn troops passing through or into an area that has been bombarded with mustard gas, so that respirators can be put on. After a cold night the officers must be continually on the watch to see whether the vapours that rise from the warming of the earth by the morning sun are charged with mustard gas, and to take the necessary precautions on the slightest detection of the characteristic smell. This smell to my mind is much more like garlic than mustard, and the use of the term “mustard gas” is purely the origination of the Tommies themselves. As a matter of fact, so as not to confuse the Yellow Cross liquid with true mustard oil, efforts were made at first to prevent the stuff from being called mustard gas. But once the British Tommy decides on a name for anything, that name it is bound to have, and as he adopted the name “mustard gas” for it mustard gas it will remain for all time. The other new material that was introduced by the Germans in the summer of 1917 and which, like mustard gas, has been in use ever since is the German “sneezing gas.” For a long time high-explosive bombardments were reported on many occasions to be accompanied with violent sneezing, which at the time was laid down to the presence in the air of undecomposed explosive from the shell. As a matter of fact the sneezing was due to the presence inside the high-explosive shell of bottles containing chemicals the chief effect of which is to cause violent sneezing when small quantities get into the air. This sneezing material, or sternutator, to give it its scientific name, in this case was a solid which is atomised into tiny particles when the shell bursts. Chemically speaking, it is called diphenylchlorarsine. This material is used embedded in the trinitrotoluene of the explosive shell in most cases, and such shells are called Blue Cross Shell, and are marked accordingly. This is the third of the present trilogy of the German coloured-cross gas shell. The sneezing gas is also sometimes mixed in with the contents of the Green Cross Shell in considerable proportions.