The first leg of the triangle was accomplished without incident. As I was starting my motor for the second stage, however, I noticed that the ignition was faulty. A spark-plug had become fouled with oil, and I had to change it before venturing up again. My companions started without me, calling out that I could catch up with them at Versailles, where they intended to lunch. I hurriedly screwed on a new spark-plug and threw my tool-bag back into the box under the extra seat, but in my hurry to be off I neglected to fasten it down. I was later to regret my carelessness. I soon found that in trying to catch up with the others I had no easy task before me. The day was well advanced, and the "remous" which I encountered were countless. I climbed and climbed. To no avail. The cloud ceiling was at eighteen hundred metres, and I could not escape the "remous" so low. The country below me was all wooded and interspersed with lakes both large and small. There was not a landing-place in view. Suddenly I felt a hard blow on the back of my head and a weight pushing against me. "Ça y est," I thought; "the machine can’t stand the buffeting and has given way." I ventured a look back. To my surprise, everything seemed intact—everything except the observer’s seat, which was leaning against my head! It was the seat which I had forgotten to hook down at Châteaudun! I was greatly relieved, and fastened it back into place. Just then I came within sight of Versailles. I looked for the aviation-field at which I was supposed to land. Instead of one I saw three, lying about two miles apart. This was indeed a puzzle. From the height at which I was flying I could not make out which was the school. I picked out one which I thought should probably be the haven of refuge for my storm-tossed aeroplane and spiralled down. I climbed out of my machine. No one seemed to be about. No mechanics ran out to assist me, as is usually the case at the schools. "It must be the luncheon-hour," I thought, "and all the mecaniciens are at déjeuner." I glanced over to where the machines were ranged in line. To my surprise, they were not of the model I had seen at Pau and Chartres, but the latest and fastest "avions de chasse." Somewhat uncertain as to my whereabouts, I walked over to the office. I was not left long in ignorance of my error. I had landed on a secret testing-field, access to which was obtained only by special permit. The sergeant advised me to lose no time in leaving, for if the captain saw me I would be speedily punished in accordance with the military regulations. I needed no second urging, and within five minutes I was on the right field, explaining to my comrades why I had been so long rejoining them. It seems that they had experienced a very pleasant flight all the way, for the hour’s start they had had over me had enabled them to escape most of the "remous," which are always at their worst in the middle of the day.