"The gallant _clairon_, however, did not wait for the word of command. As soon as he realized the danger, he tore off his protecting mask, sent his anguished appeal to his comrades in the rear and then lurched forward to die an agonizing death, though not in vain, for his brave deed had saved the day." [Illustration: _Courtesy of "Illustrated London News."_ WHEN HOODED DEMONS TAKE THE TRENCHES. British at Loos charging down on Germans first line. Note the two style of bombs and the Germans surrendering a machine gun. Also note the changed type of British gas masks.] "Great!" cried Horace, his eyes shining. "Great, indeed," echoed the veteran, "great, but awful. That a man's life should depend not on his courage, not on his skill, not on his power, but on a piece of saturated gauze before his nose--that is awful, and it is not war." "But masks are needed!" "More than ever," the veteran agreed, "for since that time the Germans have invented three different kinds of asphyxiating gas: the gases which have a suffocating effect, so that men die from strangulation, mainly carbonic acid and nitrogen; the poisonous gases, in which men are killed by reason of the poison of the fumes, such as carbon monoxide and cyanogen; and the spasm gases, in which men are killed by the muscular and nervous spasms set up by the gases, such as chlorine, sulphuric acid and phosgene.[21] One of our men, who was a chemist in civil life, told me all about it." "Which were the gases used at Ypres, where the poison gas business first began?" "Chlorine and bromine," the other answered, "so this chemist chap told me. They get the chlorine by passing strong currents of electricity through sea-water by some process he explained but which I couldn't understand; and the bromine is a by-product that they make from the Strasburg salts. But there's some other gases like sulphurous anhydride and carbonyl chloride that I don't know much about." "Did you find out how it is that the masks really prevent poisoning?" the boy asked. "That's simple enough. Chlorine and bromine have what this chemist fellow called an 'affinity' for alkalies, and the gas combines with the alkali somehow, so that all the poisonous effect is lost. French, English and German masks are different in shape, but the idea is the same. The Germans have a mask which fits over the nose and mouth, filled with absorbent cotton treated with hyposulphite of sodium or sodium carbonate. The French and English have a mask that covers the whole head and which can be tucked under the collar of the tunic.