One of the longest flights I made was to Tours. Since then I have often thought how strange it was to be flying over this historic region of France. We took it as a matter of course, but what would the ancient heroes of France have thought had they seen us? One week we were over Bourges, called the source of the French nation, for it was from here that the Duke de Berry sallied forth and conquered the English hosts, bringing to a close the struggle which had lasted for a century. The next week we were over Lorraine and the châteaux of the Bourbon kings, who did many great deeds, but had surely never thought of flying. The lectures which we attended every day were extremely important. The first subject covered had reference to artillery-fire and the theory of trajectories. It is essential that aviators be familiar with the parabola described by the shells fired by cannon of various calibers. If they are not, some day they may unconsciously fly in the very path of shells sent by their own guns and be killed by projectiles not meant for them. The "seventy-five" field-guns, when firing at long ranges, have to elevate their muzzles so much that their shells describe a high parabola before they explode over the enemy’s trenches. The very heavy shells, on the other hand, like those of the 420-centimetre French pieces and the famous German "Big-Berthas," rise to a point almost over their target and then drop suddenly. Aviators must become familiar with this and with a hundred other peculiarities of artillery-fire. When flying over the front it is too late to acquire this knowledge. Information has to be gained beforehand or you stand the chance of being annihilated with your machine. An aviator I know involuntarily got into the path of a seventy-seven or seventy-five caliber shell. He is alive to-day, but he lost his left foot in the "collision." He just managed to come down within our lines before he had bled too much to recover.