The final examination for the second brevet involves the dreaded "vrille," or tail-spin. For many years any aviator who engaged in a vrille was given up for lost. Even to-day many aviators are killed attempting to master this most important trick. Yet it has to be learned, for in modern aerial warfare it may sometime be the one manoeuvre which will enable you to escape from an assailant or make a sudden attack. The modern aeroplane is so stable that when it is made to dive it always attempts to rise and resume its flight. In the "vrille," on the other hand, this resistance is overcome, and the machine spins down with incredible rapidity. The beginner usually commences by making one turn. He allows his machine to lose its speed and slip off on the wing. After engaging in a spiral, instead of continuing he then resumes his flight. The second time two turns have to be made. More and more are made until the pilot feels that he has mastered the trick to his satisfaction. The first turn is usually made very slowly, but after that the speed increases with each succeeding turn until the machine is spinning on the corner of one wing as an axis. I have seen the more brilliant pilots at the front make as many as seven or eight turns, while they fell as far as five thousand feet. Every time I have seen any one doing a "vrille" I have thought of the young lieutenant who was killed at Pau when I attended the school for the first time. What are dangers for the beginner, in the hands of the expert become weapons. On completing this final course the pilot has learned everything that his instructors can teach him. It remains only for him to prove that in action he can avail himself of all the tricks that he has mastered. He has a machine that can manoeuvre to the best advantage, and he will enjoy a superiority which he never possessed with the heavier Farman biplane. Often I thought of this when flying over Verdun in the artillery machines. The little Nieuports seemed to circle about with such ease, doing whatever they pleased, while we lumbered about in constant danger of being attacked by some fast-flying "Fritzie" from the enemy’s lines. The principal task assigned to our "avions de chasse" is to keep the German airmen away from the French lines, and of attacking them when the opportunity offers. From an altitude of about thirteen thousand feet the Nieuports maintain a constant vigil. Although so small they are in fact the protectors of the larger artillery and reconnoissance machines. Far within the German lines several of the enemy’s artillery biplanes are flying low. Farther up their fighting planes are waiting for an opportunity of coming over to attack the French. The shrapnel-puffs from our own guns reveal that some one is crossing our lines. A German artillery machine is coming to make a "réglage." One of the Fokkers is flying high above it, but the Nieuports are doing "ceiling work" and will look out for the intruders.