So, when, looking at Neuville-Saint-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 torturous, narrow underground routes from one row of houses under 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 cracking of rifles. The French had evidently advanced across the space between the houses to finish the work of their mine. When one goes to view the work of these mines afterward all that one sees is a great round, smooth hole in the ground--sometimes 30 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 correct mathematical calculation to place them. 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-Saint-Vaast. A French aeroplane soon appeared, and the German one made off rapidly. They usually do, as most German war planes are too light to carry anything but rifles and bombs; French machines, while slower, all have mitrailleuses. A fight between them is unequal, and the inequality is not easily overcome. 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 little feathery white clouds suddenly appeared as if some giant invisible hand had just put them there--high up in the sky. Another appeared; then another. Several dozen little white clouds were vividly outlined against the blue before the French machines, all untouched, turned back to their own lines. The soldier with us suddenly threw himself face down on the ground; a second after 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.