Rifle grenades are a form of bomb on the end of a stick that fits into the muzzle of the rifle and is then discharged by means of a blank cartridge. They are effective only at short distances. Indeed, even with trench mortars, the projectiles can seldom be hurled more than four hundred yards, so that they are almost always used on the fire trenches and are never directed to trenches farther back. CHAPTER IX GAS AND LIQUID FIRE A new and deadly form of warfare is the use of GAS. Until April, 1915, we knew nothing about it and then we had to face it to our great cost. We had no masks and no apparatus of any kind to help us combat it. Having been taken by surprise in an engagement that almost cost us Calais, we set to work to devise means to counteract it. The method adopted is the helmet, made of cloth, and very much like a fireman's smoke helmet. It has large goggles similar to the ones that motorists wear. The cloth is kept saturated with a solution of ammonia which acts as a neutraliser of the chlorine gas. A tube passes through the cloth into the mouth, and through this tube the air from the lungs is breathed out. It is, of course, fatal to inhale air through it, and all the air that is breathed in has to be inhaled through the cloth of the helmet. The importance of training the soldier to be able to meet gas cannot be overemphasised. He should be drilled frequently with the helmet on to accustom him to the feeling of it, and alarms should be sounded from time to time to teach him to don the helmet as rapidly as possible. In some of the military schools in France the men were actually taken without helmets into chambers where there was just enough gas to make them realise it was there, and were then sent into other chambers with a "deadly" mixture of gas with their helmets on. This training makes them realise the importance of helmets. Many forms of helmets have been used from time to time, and in this matter as in many others we have learnt from our enemies. For the most recent British mask contains the "nosebox" or "beak" which conforms to the German model. As in most other things, simplicity is to be desired where it can be combined with effectiveness, and it is the simplicity of the cloth helmet with the tube that even to-day commends it to many critics above the "box" forms--those that require an independent supply of oxygen. Where men such as gunners are liable to be exposed to fumes for some considerable length of time, either from cylinder gas or from shells or even from tear shells, or must continue at their posts at any costs, an independent fresh air supply is necessary.