On every side of us were the French artillery biplanes. They were hovering over the German lines like gulls, continually wirelessing back the ranges to their batteries. High above us circled the little Nieuports on guard, to protect us and to prevent the Fokkers and aviatiks from crossing over our lines. Everywhere were little white puffs, which seemed to follow the machines about. I watched them, strangely fascinated and amused, until my pilot informed me that these were caused by exploding shrapnel from the enemy’s anti-aircraft guns. Then I noticed with uneasiness that the same puffs were also following us. My interest in the little white puffs from that moment assumed quite another character. I listened for the sharp crack of their explosions, but all I could hear was a dull "whung." The thought that very few machines are really brought down by shrapnel was a bit reassuring, but I must admit that when the enemy is sending them on all sides of you, you do not feel like giving much credence to what others may have told you. Presently my attention was called to the lines of German captive balloons, which are moored some miles behind their first-line trenches. Several aeroplanes stood guard over them, and as we knew that they were armed and that we on this occasion were not we decided to turn back. I made several of these trips over the different positions on our immediate front. By the time my own machine arrived I was thoroughly familiar with the sector and also with the main dangers to be encountered by aviators over the battle lines. The first precaution I learned was—always, when landing, to unhook the belt that held me in my seat. This is one of the most important things to remember at the front. The fields are not always in the best condition, and the slightest obstruction may cause an unexpected crash. If you are in an artillery pusher-machine when this happens you are invariably crushed under the motor, unless your belt is unfastened, when you are usually thrown clear. [Illustration: "Everywhere little white puffs seemed to follow the machines about."]