=High Explosive in Projectors.= When these are burst by the hundreds on a small area everything movable is blotted out. Thus concrete machine gun emplacements, lookout stations, bomb-proofs and wire entanglements are destroyed, trenches filled up, and the personnel annihilated. This was amply demonstrated on the few occasions when it was actually used at the front. The American Infantry, wherever they saw it tried out, were wild to have more of it used. The German was apparently equally anxious to have the use stopped. It is, however, one of the things that must be reckoned with in the future. It means practically that No Man’s Land in the future will be just as wide as the extreme range of these crude mortars—and here a word of caution. While efforts have been made to increase the range of these mortars, whether of the Livens’ projector or Stokes’ variety, no further increase will be attempted when that increase reduces the speed of firing or the efficiency of the projectile. In other words results depend upon large quantities of material delivered at the same instant on the point attacked, and if this cannot be obtained the method is useless. For this reason these mortars will never be a competitor of the artillery. The artillery will have all that it can do to cover the field within its range—beyond that reached by the mortars. =Phosphorus in 4-Inch Stokes.= Phosphorus will be used largely by gas troops, but only in the 4-inch or other Stokes’ mortar that may be finally adopted as best. The Livens’ projector carries too great a quantity, and being essentially a single shot gun, is not adapted to keeping up a smoke screen by slow and continued firing, or of being transported so as to keep up with the Infantry. Phosphorus has also very great value for attacking personnel itself. Any one who has been burned with phosphorus or has witnessed the ease with which it burns when exposed to air, wet or dry, has a most wholesome fear of it. The result of it in the war showed that the enemy machine gunners or other troops would not stand up under a bombardment of phosphorus fired from the 4-inch Stokes’ mortar—each bomb containing about seven pounds. =Thermit.= Thermit is used in the same way, and while the idea of molten metal, falling upon men and burning through clothing and even helmets, is attractive in theory, it proved absolutely worthless for those purposes on the field of battle. It was found impossible to throw sufficiently large quantities of molten metal on a given spot to cause any considerable burn. In other words, the rapid spreading out and cooling of the metal almost entirely ruined its effectiveness, except its effect on the morale. This latter, however, was considerable, as one might judge from seeing the thermit shells burst in air. For this reason thermit may find a limited use in the future. THE SPREAD OF GAS