ON CHEMICAL WARFARE. 393 



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Chemical Warfare. By Brigadier- Greneral H. Hartley, C.B.E., M.C. 

 (Ordered by the General Committee to be printed in exfentio.) 



One of the most striking contrasts between the late war and those which 

 preceded it is the rapid development of scientific and mechanical methods of 

 warfare, which resulted from the concentration of most of the scientists and 

 engineers of the world on war problems. Of the new developments none was 

 more far reaching in its effects on land than the introduction of gas and smoke, 

 and on the sea smoke played an important part in naval tactics. 



The object of this paper is to sketch the development of gas warfare, to show 

 the ways in which gas proved itself a valuable weapon, and to describe the nature 

 of the problems with which British chemists were confronted and their success 

 in solving them. 



First Use of Gas by the Germans. 



Gas was employed during the war in two ways, in cylinders and in projectiles. 

 In the first method of attack, a gas such as chlorine, which could be liquefied at 

 atmospheric temperatures by a moderate pressure, was compressed in large steel 

 cylinders from which it could be discharged rapidly just as from a soda-water 

 syphon. These cylinders were taken into the trenches and large numbers were 

 discharged on a continuous front when the wind would carry the gas over the 

 enemy's lines. In the second method, part of the explosive charge of a shell 

 was replaced by gas, which could thus be used independently of the wind 

 direction. Both methods were introduced by the Germans almost simultaneously 

 in April 1915. 



Two reasons have been given to explain their introduction of gas into warfare. 

 Firstly, when the German supplies of high explosives were found to be insuffi- 

 cient after the battle of the Marne, they began to consider the possibility of 

 increasing their total output of shell by using gas which could be manufactured 

 without interfering with the production of high explosives. Secondly, pre- 

 liminary bombardments with H.E. and shrapnel had failed to guarantee the 

 success of an infantry attack ; the need was felt of some new types of shell to 

 supplement the action of the old. Bat there was another and more powerful 

 reason for the introduction of the new weapon — the knowledge of the advantage 

 to be gained by a surprise use of lethaA gas contrary to the Hague Convention. 



The first German cylinder attack was made by means of chlorine on April 22. 

 1915, against the French on a frontage of about four miles in the north of the 

 Ypres salient. The effect of a cloud of chlorine on unprotected troops is easily 

 imagined : for some distance behind the line all were killed or rendered incapable 

 of offering any resistance. It was a great opportunity for a decisive stroke, 

 but the Germans failed to take advantage of it. The quantity of gas used was 

 too small to make it effective to a great distance, the front of discharge was com- 

 paratively short, and the Germans failed to exploit the partial success they gained. 

 Two days later a second cloud attack was made on the British front against the 

 Canadians with similar results. In May four more attacks took place, but in 

 these our troops were protected partially with hastily improvised respirators 

 and suffered much less severely. After May no more cloud attacks were made 

 on the British front until December 19, 1915, when an attack of a more formidable 

 nature was made to the N.E. of the Ypres salient. Cylinders were used con- 

 taining a mixture of phosgene and chlorine, and a much higher concentration of 

 gas was obtained. However, our troops were equipped with a respirator that 

 gave adequate protection, and only those who were surprised or who failed to 

 adjust their respirators properly, became casualties. Five similar cloud attacks 



