"Still," responded the doctor, trying to find some hope in the outlook, "we have the advantage of being on the defensive. I've read, somewhere, that it takes three times as many men to drive an attack as to hold a line of defense." "That is true," agreed the master. "They can't be more than three to one," said the doctor, "so as fast as they come, we'll smash them." "Perhaps we might have a better chance," the old reservist said, doubtfully, "if General Leman and our Third Division were here. But it's not the German soldiers of which I'm afraid, but these new howitzers." "Why?" asked the doctor. "Isn't a howitzer a gun? What's the difference between them, anyway?" "I'll show you the difference in a minute," the master replied, "but I want, first, to give you a clear idea of one of our big forts, so that you can realize the problem that the Germans must tackle. Each of the six main forts around Liége is built in the form of a triangle, each is placed in a commanding natural position, and each, in addition, is approached by a steep artificial mound, in the interior of which lie the works of the fort. At the top of the earth slope, the edge drops suddenly into a deep ditch, of which the counterscarp is a massive masonry wall topped with wire entanglements. The entire earth slope and wall is exposed to the guns of the fort, throwing shrapnel, and to fire from machine guns and rifles." "Before the Germans get a footing in the fort, then," said the doctor, "they will have to storm a stretch of ground absolutely riddled with fire." "They will." "That means a heavy loss of life." "A terrible loss of life," the master agreed. "Moreover, even should they advance in such masses that we could not kill them fast enough and thus they should storm the slope and win the ditch, they would be in a still worse plight. Powerful quick-firing guns, mounted in cupolas at each angle of the triangle, sweep the sunken ditch with an enfilading fire. No troops could live through such an inferno of bullets. "On the main inner triangle is the infantry parapet, shaped somewhat like a heart, pierced for rifle fire and with machine-gun emplacements at the angles. In the hollow of that heart-like space rises a solid central mass of concrete, on and in which are the shelters and gun cupolas. The mortar cupolas rise from the floor of the hollow, outside the central mass. These are invisible to the foe until raised by machinery within, when they command the entire neighborhood and can fire their 6-inch shells in any direction." The doctor rubbed his hands briskly. "If that's the way our forts are built," he said, "and if they are well provisioned and have plenty of ammunition, we ought to be able to snap our fingers at the Kaiser. All we have to do is to wait for the Germans to come and shoot them down by thousands. They'll go packing back to Germany quick enough if we give them a reception like that."