In the western area of the theater of war, in France and Flanders, where whole armies were deadlocked, facing each other for weeks without shifting their position an inch, such trenches become an elaborate affair, with extensive underground working and wing connections of lines which almost constitute little fortresses and afford a certain measure of comfort. But where we were in Galicia at the beginning of the war, with conditions utterly unsteady and positions shifting daily and hourly, only the most superficial trenches were used. In fact, we thought ourselves fortunate if we could requisition enough straw to cover the bottom. That afternoon we had about half finished our work when our friend the aeroplane appeared on the horizon again. This time we immediately opened fire. It disappeared, but apparently had seen enough, for very soon our position was shelled. By this time, however, shrapnel had almost ceased to be a source of concern to us and we scarcely paid any attention to it. Human nerves quickly get accustomed to the most unusual conditions and circumstances and I noticed that quite a number of men actually fell asleep from sheer exhaustion in the trenches, in spite of the roaring of the cannon about us and the whizzing of shrapnel over our heads. I, too, soon got accustomed to the deadly missiles,--in fact, I had already started to make observations of their peculiarities. My ear, accustomed to differentiate sounds of all kinds, had some time ago, while we still advanced, noted a remarkable discrepancy in the peculiar whine produced by the different shells in their rapid flight through the air as they passed over our heads, some sounding shrill, with a rising tendency, and the others rather dull, with a falling cadence. A short observation revealed the fact that the passing of a dull-sounding shell was invariably preceded by a flash from one of our own cannon in the rear on the hill, which conclusively proved it to be an Austrian shell. It must be understood that as we were advancing between the positions of the Austrian and Russian artillery, both kinds of shells were passing over our heads. As we advanced the difference between shrill and dull shell grew less and less perceptible, until I could hardly tell them apart. Upon nearing the hill the difference increased again more and more until on the hill itself it was very marked. After our trench was finished I crawled to the top of the hill until I could make out the flash of the Russian guns on the opposite heights and by timing flash and actual passing of the shell, found to my astonishment that now the Russian missiles had become dull, while on the other hand, the shrill shell was invariably heralded by a flash from one of our guns, now far in the rear. What had happened was this: Every shell describes in its course a parabolic line, with the first half of the curve ascending and the second one descending. Apparently in the first half of its curve,