This was pretty well the position of things in July of last year, when the German use of gas shell underwent a radical development due to the advent of the so-called mustard gas. So much has been written about this gas and so many mis-statements have been made concerning it that it is as well for the public to understand what mustard gas is, what it can do and what it cannot do. On the one hand, it has been credited with such impossible potency as would make it wonderful that any Allied soldiers remain at all. On the other hand, it should be realised that in mustard gas the Germans possess a very powerful weapon of war and one which they are using to a very considerable extent. In the first place let it be said that mustard gas is not a killing gas like Green Cross, but that it is of the persistent type, like the older lachrymators. Unlike the lachrymators, however, its effects are not transitory and a man put out of action by mustard gas is going to be a casualty for several weeks and perhaps longer. Mustard gas principally affects the eyes and the lungs, but in a very strong vapour or in contact with any of the actual liquid from the shell a man’s skin may be burned very severely--even through his clothes. More attention has been turned to this blistering effect of the gas than to anything else, but as a matter of fact the blistering is of secondary importance and in itself does not result in the loss of many men to the line. Of course one has to be very careful. It is foolish, for example, to lean up against sandbags that have been spattered with the liquid or to sit in a mustard-gas shell crater. Sooner or later the skin underneath will develop a severe and possibly extensive blister, which is very painful and certain to last some time. These burns are not dangerous, but they are most uncomfortable, to say the least, especially as they are most easily produced on the more tender parts of the skin. Great excitement was caused at first among the Highland regiments because the story was spread about that the Scots were particularly susceptible to the mustard gas because of their attenuated clothing. As a matter of fact the kilt doesn’t seem to be a source of danger at all, and Highlanders are burned no more frequently than others. Possibly the continued exposure of their legs hardens them.