Map-reading and navigation were the next subjects we studied. First we were taught how to read a map, how to judge the height of hills and the size of towns, so that when flying we would know at a glance just where we were. This, we later appreciated, is a very important matter. When passing through clouds or mist an aviator may become momentarily lost, and the instant he again sees the ground he must locate on his map the country he views or else land and ask where he is. Aerial navigation may not be as complicated as that employed by mariners upon the high seas, but it is not easily mastered by any means. One must learn to calculate the direction a straight line takes between two points, and translate this direction into degrees on the compass. Secondly, and more important, is the estimation of the drift caused by the wind. If the wind is from the west and the pilot is attempting to go north, the machine will go "en crabe" (sideways like a crab). The machine will be pointing north by the compass, but in reality it will be moving northeast. After the pilot has laid out his course on the map, and is tearing through the air, he must immediately take into consideration his drift. By watching landmarks selected beforehand the drift is calculated very quickly. The course by the compass is altered, and, though the machine is speeding due north, the compass informs the pilot that he is pointing northwest, a fact very confusing for a beginner. *LEARNING TO FLY* During the lecture course we always spent several hours a day on the aviation-field. We were not allowed to fly, but our presence was insisted upon. We would observe the things to avoid, so that when our turn came to go up we should be familiar with all the dangers. Every start, flight, and landing was made a subject of special study. Every time a pupil made a mistake his fault was explained to us, and we were usually impressed with the fact that he had barely escaped a bad smash and perhaps death. The pupils who made the mistakes, were immediately made examples. If the fault was corrected they escaped with a long and loud lecture for the benefit of the onlookers, but if, on the other hand, an accident followed the mistake the offenders were immediately punished with a ten days’ "consigne." If a pupil continued to make mistakes he was "vidé," and sent back to his former regiment.