By this time the British Army had been fitted out with the celebrated box respirator--a respirator of particular interest to Americans, as it was the type adopted for and at present in use in the American Army. A short description of it will not be out of place. The principle of the respirator is to have a box filled with chemicals and attached by a flexible tube to a face piece or mask, which fits closely to the face. All air breathed by a man must therefore pass through the chemicals, and these are so chosen that they will absorb any and every poison that may be present in the atmosphere at the time. In order to keep the air pure in the mask and to have a double line of protection a man breathes through a special mouthpiece and has his nose clipped. So even if the face piece, which is made of rubber cloth, should be torn or damaged in any way the soldier is perfectly safe as long as he does not attempt to talk--that is, if he keeps his nose clipped and does not remove the mouthpiece from his mouth. The respirator is not only active against a diversity of poisonous gases but it will keep out very high concentrations of gas for many hours. One of the most misleading statements made about gas masks--sometimes by newspaper men and consequently given wide publicity--is that such and such a mask will stand up for so many hours against gas. It is a very natural thing to want to know or to state how long your respirator will last, but without stating what concentration of gas is being talked of it is impossible to give such definite information about any mask. It simply depends on the amount of gas there is in the air. But the box respirator if kept in good condition and properly used is guaranteed to keep out German gas continuously for many hours, even in concentrations which it is quite impossible for the boche to maintain in the field. In the American modification of the box respirator the absorptive power of the chemicals used is even greater than in the British box, and this makes it the best respirator in the world, which is very reassuring for those who have to make use of it. The box respirator is contained in a haversack and is carried slung on the shoulder until such time as the soldier comes into the forward areas, where it must be carried tied up on the chest ready for instant adjustment in case of need. As I mentioned before, it can be put on in six seconds from the word “go,” and once a man is practiced in wearing it he can walk, run, shoot, dig, speak or do anything but eat and smoke in it; and this for long stretches at a time. I know many cases where men have been forced to wear masks literally continuously for more than eight hours; and much longer periods than this, with perhaps short intervals of rest in protected dugouts or in unaffected areas, are common.