The reasons why explosives are more likely to be effective than poison on a town are as follows. Houses are far more vulnerable to explosives than earthworks, and do far more damage to their occupants in collapsing, besides being inflammable. And, on the other hand, they contain far more refuges which are nearly gas-proof. A shut room on a first or second floor would be nearly proof against gas released in the neighbourhood if it had not got a lighted fire to drag contaminated air from outside into it. Moreover, civilians could, and would, rapidly evacuate an area which has been heavily soaked with mustard gas, whereas soldiers have to stay on at the risk of their lives. Gas-bombs would certainly be far less effective than high-explosives on a town whose inhabitants were provided with respirators, probably even if they were unprovided. But, so long as London is undefended in this respect, it constitutes a standing temptation to any power desirous of making this kind of experiment. Judging from experience, there is no doubt that a gas or smoke attack from the air would occasion a first-class panic. The introduction of each new chemical weapon produced great terror, as did even such a militarily unimportant (though cruel) weapon as the _Flammenwerfer_ (flame-projector). This was certainly due to ignorance. The French Colonial troops who were caught in the first cloud-gas attack were far more frightened than the Canadians, and appear to have had far more casualties, although they mostly ran away: which the Canadians did not. For the Canadians made some attempts to improvise respirators, and almost any damp fabric will reduce the concentration of chlorine passing through it to half or less. They also breathed less because they did not run. As a matter of fact, a most efficient respirator against chlorine (though whether against mustard gas I do not know) can be made by knocking the bottom off a bottle, filling it with loose earth, placing its neck in the mouth, and breathing through it. Very great alarm was caused by the first mustard gas bombardments in France, as no one had ever seen anything resembling the blisters it caused. But very soon familiarity bred contempt, or even liking, for aeroplanes dropped sheaves of pamphlets explaining how any soldier tired of the war could become a casualty without danger either of death or detection by allowing earth contaminated with mustard gas to touch the skin or the clothing. A good many wound-stripes were earned by this simple and up-to-date method, though, as we had the superiority in the air and the German soldiers were both more tired and more confiding than our own, the German casualties from this cause were probably still greater. But let us tell our civilian population before and not after they are attacked with blistering gases that the blisters produced are considerably less dangerous than measles. It was predicted during the war that the