Loss of speed—"perte de vitesse," the French call it—is the most common and probably the greatest danger an aviator meets with—it is his "bête noire." There is a minimum speed capable of holding an aeroplane in the air which varies inversely with the spread of the wings. While in line of flight, the force of the motor will maintain the speed, but when the motor is shut off and the pilot commences to volplane the force of gravity produces the same result. There are two ways of knowing when you are approaching the danger-point—by closely watching the speed-indicator and by feeling your controls. The moment the controls become lifeless and have no resistance you must act instinctively and regain your momentum, or it is all up with you. While climbing you may lose speed by forcing the motor and climbing too rapidly. When a "perte de vitesse" is produced the aeroplane "goes off on the wing," sliding down sideways in such a manner and with such force that the rudders cannot right you or that the propeller cannot pick up your forward speed. This can happen also if, when making a vertical turn, the speed is not sufficiently increased to carry you around the corner. Occurring near the ground a loss of speed is certain to result in a smash-up. If high in the air a "vrille," or tail spin, is generally the result. By this is meant coming down in a whirlpool, spinning like a match in the waste of a basin. The machine takes as a pivot the corner of one wing and revolves about it. The first turn is very slow, but the speed increases with each revolution. The only hope of escape is to dive into the centre of the whirlpool. Even then, if the motor is turned on, the planes will fold up like a book. Among the accidents to beginners this, next to faulty landing, is the most common. [Illustration: A Morane-Parasol.] I witnessed one very sad example. A young lieutenant had just been brevetted and was ready to leave the school. Just as he was saying good-by to his comrades, a "Morane Parasol" was brought out on the field. These machines are very tricky and dangerous. He had never piloted one, but wanted to show off. The monitors begged him not to take it up, but he insisted on doing so. When he had reached an altitude of about five hundred metres he shut off his motor to come down, not realizing that monoplanes do not volplane well. He did not dive enough and had a "perte de vitesse." The machine slipped off the wing. We all held our breaths and prayed that he would recover control before he engaged in the fatal corkscrew spiral. Our hopes were of no avail. The machine started to turn, and approached the earth spinning like a chip caught in a whirlpool. I turned my back, but I could hear the machine whistling through the air till it came to the ground with a sickening crash.