We listened to a technical but most interesting exposition by the Artillery Captain of the most up-to-date methods of firing at aeroplanes, including the progressive and retrogressive systems, and then sped away to the aviation field some ten or fifteen kilometres distant. We found the aviation squadron on a very large field near the top of a gradually sloping bare hill, comfortably installed, the machines in their great hangars, the aviators in their small tents. The whole organization was especially adapted for mobility. In one hour, at need, the field would have left on it not a man, a stick or a shred of the encampment. Hangars and tents would be careering along some highroad, neatly folded in the big aviation lorries that stood handy, mechanics would be sitting on the box seats or have their legs dangling over the tail-boards, while pilots and observers would waft themselves more comfortably by air to their new camp site. The Captain of the "esquadrille" showed us, with quite pardonable pride, his "avions de réglage"--planes carrying no bombs or machine-guns, but equipped with wireless, which are used to correct the fire of artillery, and his "avions de chasse" or hunting-planes equipped with bombs, a machine-gun and a Winchester carbine. Some of these had the pilot sit behind and the observer in front operating the machine gun over the bow. Others had the pilot in front and the observer behind, in which case the observer, standing up, operated the machine-gun over the head of the pilot. Finally he showed us a splendid new Caudron biplane having two independent motors and two traction screws in front, so that if either motor were put out of business the plane could continue flying on the other. I was so enthusiastic about this machine that the Aviation Captain turned to me and asked casually, "Would you perhaps like to go up and take a 'petite promenade' in the Caudron?" Would I? It did not take me many fractions of a second to impress on him that I certainly would. But here Captain d'A---- demurred. It was, he said, absolutely forbidden that any one should go up in army aeroplanes except aviators on military duty. Those were the strict army regulations. He was quite right and entirely justified in his attitude. But Captain F----, who was a good sport and had become quite a chum of mine, said, "Oh, let him go up. After all, the Swiss Military Attaché went up the other day. I'll take the responsibility." And as he was in immediate authority while we remained with the 5th Army, Captain d'A---- good-naturedly shrugged his shoulders and let it go at that.