Subparagraph D. With reference to paragraph 17 your cablegram 165 and paragraph 2 my cablegram 181, Tissot has constructed simpler model of his mask for attachment to any box. Have ordered 6 which will be completed in two weeks, 3 of which will be forwarded at once. A simple type such as this may prove useful for large number of troops. Letter of permission to manufacture Tissot masks being forwarded. Subparagraph E. With reference to paragraph 8 your cablegram 143, and paragraph 4 your cablegram 247, in considering charcoal and other fillers for canister of box respirator it should be remembered that the front is very damp, the air being nearly saturated during greater part of winter, fall and spring. This cable is given in full to show that not later than November 4, 1917, it was known in the United States not only what gases would be required but also in what shells, bombs, guns and mortars each would be used. While a small quantity of Vincennite was recommended in this cable, another cable sent within a month requested that no Vincennite whatever be manufactured. This decision as to gases and guns in which they were to be used, while very progressive, proved entirely sound and remained unchanged, with slight exceptions due to new discoveries, until the end of the war. Without a thorough understanding of tactics a proper choice of gases could not have been made. This fact emphasizes the necessity of having a trained technical army man at the head of any gas service. Due to the absence of a Chemical Warfare Service in the United States at this time, a very great deal of the information sent from France, whether by cable or by letter, never reached those needing it. =Smoke.= About the first of December after a study of results obtained by the British and the Germans in the use of smoke in artillery shells for screening purposes, the Gas Service decided that much more smoke than had been stated in cable 268 to the United States was desirable. The General Staff, however, refused to authorize any increase, but did allow to be sent in a cable a statement to the effect that a large increase in smoke materials might be advisable for smoke screens, and that accordingly the amount of phosphorus needed in a year of war would probably be three or four times the one and a half million pounds of white phosphorus stated to have been contracted for by the Ordnance Department in the United States. This advanced position of the Gas Service in regard to smoke proved sound in 1918, when every effort was made to increase the quantity of white phosphorus available and to extend its use in artillery shells including even the 3 inch Stokes’ mortar. [Illustration: FIG. 16.—Troops Advancing Behind a Smoke Barrage (Phosphorus).]