Alfred understood why so much care had been taken to cover up the guns, for the Germans had guns which would reach as far as the 75's, but the question was how to locate the batteries. In this particular the French were superior, as well as in the ability to handle the guns rapidly and accurately, for it must be admitted that the French had easily taken the lead in the use of heavy ordnance. It did not take long to fire forty shots. There was only a short cessation after the prescribed number had been let loose. The Farman machine came up close. It signaled. "That battery has been put out of commission," said Alfred. The lieutenant nodded approvingly and with a great show of pleasure. "Two degrees to the left," shouted the lieutenant. [Illustration: _Peculiarities of Trajectories_] Crack! crack! bang! spoke out the pieces as before. And now it seemed as though the whole hillside shook with the resounding roar. Alfred and Ralph, as well as the officers, were on a slight elevation, which enabled them to look across the valleys, but the gunners who were firing could not see, because they were too far down behind the crest. The boys had been too busily engaged to notice that all along that low range, of which they occupied but a small part, the artillery had taken up positions during the night, and that more than two hundred guns were now commencing and with frightful execution carrying out that most terrible of all forms of modern artillery warfare, the barrage fire. "We heard about that before we left Verdun," said Ralph. "Is that what is going on now?" he asked. The captain nodded. "You will notice that the guns are now pointed at an angle which will carry the shell the farthest," he said. "Is that the forty-five degree angle?" asked Alfred. [Illustration: _Peculiarities of Trajectories_] "Yes; if we elevate the guns the trajectory will be higher, but the shot will fall short of the maximum; if the gun is depressed the shell will fall nearer to the gun. After we have demolished everything at long range, the forward end of the gun is lowered and a certain number of shots fired, each gun swinging around a little to the right and to the left, so as to reach all the spaces between the guns. Then the gun is depressed still more, and at regular intervals this is repeated until every foot of space from the longest range to the shortest in front of us is searched out." "But while the shots are coming closer and closer to our front lines won't the Germans come up and occupy the spaces, just as before?" asked Ralph. "That is just what we want them to do," replied the lieutenant. "Why so?" asked Alfred. "Because, at a given signal, the guns are again raised at the highest angle, and the result is that all who have ventured to come forward, are trapped, and will be caught by the next sweep of shots as they are brought forward," answered the lieutenant.