394 REPORTS ON THE STATE OF SCIENCE. — 1919. 



took place in 1916, each consisting of a short discharge of a very high concen- 

 tration, so as to obtain the maxinuim effect of surprise. No serious attempt was 

 made to follow up any of these later discharges with an infantry attack, as our 

 troops were now fully protected and the opportunity for a ' break through ' 

 offered by the earlier gas attacks was not likely to occur. The last German 

 cloud attack on the British front was on August 8, 1916. 



BritisJi Use of Cloud Gas. 



Immediately after the first use of gas in April 1915, steps were taken for 

 effective reprisals on our part. The Special Companies R.E. were formed under 

 the command of Major (later Brigadier-General) C. H. Foulkes, C.M.G., D.S.O., 

 R.E., consisting largely of chemists who were specially enlisted as corporals for 

 this purpose. After seven weeks' training in France they carried out our first 

 gas attack with chlorine cylinders at Loos on September 25, 1915. After that 

 date cloud attacks were carried out frequently by us as we had the advantage 

 of the direction of the prevailing wind, and the operations of the Special Com- 

 panies proved so successful that they were soon expanded into a Special Brigade 

 R.E. in which many of the original chemical corporals received commissions. 

 By the end of the war the Brigade had carried out 768 gas operations in which 

 5,700 tons of gas were liberated. Twenty-five per cent, of these operations were 

 cloud discharges, the remainder being trench mortar or projector attacks. In 

 addition the units of the Brigade were frequently employed in producing smoke 

 clouds which played an important part in infantry attacks. 



Abundant evidence exists both in captured documents and in prisoners' state- 

 ments of the heavy casualties and loss of morale which the enemy suffered as a 

 result of the operations of the Special Brigade, and their enterprise and gallantry 

 were repeatedly mentioned in despatches by the Commander-in-Chief. 



German Use of Gas Projectiles. 



The Germans employed shell containing gas on the British front al the same 

 time as their first cloud attack, the contents of the shells being crude brominated 

 xylene or brominated aliphatic ketones. Both substances cause considerable in- 

 convenience owing to their lachrymatory effect on the eyes, but have not a high 

 toxic value. As the wind was usually unfavourable for the German use of cloud 

 gas, their efforts were mainly directed to the development of the gas shell. 

 Employed in this way gas is a much more flexible weapon than in cylinders as its 

 use is far more independent of atmospheric conditions, and a much wider range 

 of substances can be used with properties suited to different tactical purposes. 

 Certain little-known organic compounds were selected as being most suitable, 

 and thanks to the technical resources of the German dye industry, a monthly 

 output was soon obtained amomiting to several hundred tons of organic deriva- 

 tives, which prior to the war had only been prepared in small quantities in the 

 laboratory. 



_ In the summer of 1916, chlormethyl chloroformate, a liquid (B.P. 105° C.) 

 with toxic properties similar to those of phosgene, was used against us in large 

 quantities during the battle of the Somme. Later this was replaced by 

 trichlormethyl chloroformate. a similar liquid (B.P. 128° C), which was used 

 until the end of the war as the well-known Green Cross shell filling. The use of 

 phosgene in trench mortar bombs also began in 1916. 



In April 1917, during the Arras battle, a variant of the Green Cross filling 

 appeared containing 50 per cent, of chlorpicrin (B.P. 112° C), a lachrymator 

 with asphyxiant properties against which the P.H. Helmet offered no protection, 

 but, as our troops were already equipped with a box respirator, the new filling 

 had no advantage over the old.' 



In July 1917, just before the third battle of Ypres, Yellow Cross and Blue 

 Cross gas shells (so named after their markings) were introduced, each of which 

 had novel properties. Yellow^ Cross shell contained dichlorethyl sulphide 

 (B.P._ 217° C), commonly known as ' Mustard Gas ' on account of its smell, or as 

 Yperite. The properties of this substance make it a most effective battle gas. 



