The importance of protection against mustard gas burns led to extensive researches being made with a view to finding a cloth which would be comfortable and porous and while stopping mustard gas would yet be sufficiently durable and comfortable to be issued to infantry troops as well as to artillery and other special troops. This, it is understood, had been achieved, just prior to the Armistice. Still more desirable would be the discovery of a chemical substance which could be applied to all uniforms and Army clothing and thus protect the regulation clothing against the penetration of mustard gas, and thereby avoid carrying extra clothing for that special purpose. PROTECTING TROOPS BY MOVING THEM FROM INFECTED AREAS As soon as it was fully realized that mustard gas persisted for several days it was decided to run complete reliefs of men into and out of areas that had been heavily shelled with mustard gas, or better still, where practicable, to completely evacuate the area. Inasmuch as the gas is dangerous to friend and foe alike, this method was comparatively safe and was used to a very considerable extent. With the warfare of movement that existed over most of the active front throughout the season of 1918, this moving of troops out of infected areas became highly important and, when skillfully done, often resulted in a great saving of troops and at the same time prevented the enemy from receiving any particular tactical advantage from his mustard gas attacks. There was one very excellent example of this a few miles to the northwest of Château-Thierry prior to the counter-offensive of July 18, 1918. At that time the Germans heavily shelled with mustard gas four or five small woods and two or three villages. It was necessary for the men to stay in these woods during the day, as they afforded the only protection obtainable from machine guns, shrapnel and high explosive. At the time this occurred American gas officers generally understood the necessity of getting troops out of a mustard gas infected area. Accordingly all began searching for places safe from the mustard gas. In one particular instance the gas officer of a regiment discovered that a portion of the woods his men were in was free from the gas, and the regimental commander, promptly following his advice, moved his troops into the free area. As a result of this prompt action the regiment had only four light gas casualties, although all told there were several hundred mustard gas casualties in this attack, the number per thousand generally being from ten to twenty times that of the thousand men just mentioned. MIXING POISONOUS GASES