Again with regard to weight, for preference he should be on the light side. There is not very much room in an aeroplane, and, for reasons with which we will deal, the machine is only capable of lifting up to a certain weight. Take into consideration that an aeroplane is often required to take up two passengers, not to mention bombs, grenades, spare petrol and a machine-gun; every extra pound of weight is of the utmost importance. His stomach must be strong, for with a weak stomach he will be liable to air-sickness. Further, he must be possessed of good health. He must not suffer from heart trouble. It has been proved by several very eminent doctors that the rise and the descent through the various altitudes of the atmosphere effect the heart greatly. Again, he must have good eyesight. This is imperative, for the best part of his work will take place at an altitude of ten thousand feet above the earth. The best age for an air pilot is between nineteen and twenty-four. The life of a pilot--that is to say, his flying life--varies from three to five years; I may say eighteen months under war conditions. Never more. The great strain on the nerves, although not felt at the time, begins to make itself apparent after two years of flying; then the pilot discovers that he is no longer so keen on going up as he was, that he gets “cold feet” more frequently than he was wont to do in the early days, that he has no longer the nerve to do the little tricks, upon the performance of which he formerly prided himself. A good air-pilot must be born so, he cannot be made. After years of experience a man may become expert in trick flying, landing, getting off, etc.; but, however long and however diligently he may strive, he can never become the equal of the natural pilot. Before applying for a Commission in either Service the aspirant to flying honors must first decide which of the two branches he wishes to take up. The two branches, by the way, are pilotage and observation. The difference between the two I will here briefly endeavor to explain. The pilot is concerned with the flying of the machine, the care of the engine, spare parts, etc., and is responsible for the general condition of the craft; also to see that it is properly tested before each flight. On the other hand, the observer has a great many subjects to learn. He must be at one and the same time wireless expert, gunner, rifle-shot, artist, photographer and map-maker. He must know something about heavy artillery. The observer in the Royal Flying Corps is given equal rank to the pilot, but can only wear a half-wing on his tunic where the pilot has full wings. In the Royal Naval Air Service observers are permitted to wear the bird on their sleeve immediately on joining. However, they are of different rank from the pilot, being either lieutenants or sub-lieutenants, Royal Naval Volunteer Reserve. CHAPTER II THE AIRMAN’S FIRST DAYS