So, when looking at Neuville-St. Vaast, I suddenly heard a tremendous explosion and saw a great mass of masonry and débris of all descriptions flying high in the air, I knew just what had happened. The French--for it is always the French who do it--had burrowed, sapped and dug themselves laboriously, patiently, slowly, by tortuous, narrow underground routes from one row of houses under the foundations, gardens, backyards, and streets to beneath the foundations of the next row of houses. There they had planted mines. The explosion I had just witnessed was of a mine. Much of the débris I saw flying through space had been German soldiers a few seconds before. Before the smoke died away we heard a savage yell. That was the French cry of victory. Then we heard a rapid crackling of rifles. That was the sign that the French had advanced across the space between the houses to finish the work their mine had left undone. When one goes to view the work of those mines afterward all that one sees is a great, round, smooth hole in the ground--sometimes thirty feet deep, often twice that in diameter. Above it might have been either a château or a stable; unless one has an old resident for guide it is impossible to know. It takes many days and nights to prepare these mines. It takes careful mathematical precision to determine that they are correctly placed. It takes morale, judgment, courage, and intelligence--this fighting from house to house. And yet the French are called a frivolous people! A cry from a soldier warned us of a German aeroplane directly overhead; so we stopped gazing at Neuville-St. Vaast. A French aeroplane soon appeared, and the German made off rapidly. They usually do, as the majority of German aeronauts carry only rifles; the French now all have mitrailleuses. A fight between them is unequal, and the inequality is not easily overcome, for the German machines are too light for mitrailleuses. Four French machines were now circling above, and the German batteries opened fire on them. It was a beautiful sight. There was not a cloud in the sky, and the sun had not yet gone. We could not hear the shells explode, but we could see little feathery white clouds suddenly appear as if some giant invisible hand had just put them there--high up in the sky. Another appeared, and another. There were several dozen little white clouds vividly outlined against the blue before the French machines, all untouched, turned back toward their own lines. Again our thoughts and actions were rudely disturbed by the soldier with us, who suddenly threw himself face down on the ground. Before we had time to wonder why a German shell tore a hole in the field before us, less than a hundred yards away. I asked the officer if we had been seen, and if they were firing at us. He said he did not think so, but we had perhaps better move. As a matter of fact, they were hunting the battery that had so accurately shown us their trenches a short time before.