Page:Popular Science Monthly Volume 92.djvu/433

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the Germans, not content with the gaso- line flares, dug two shallow trenches, both five hundred yards long and set two hun- dred yards apart inside the "L." These they lined with bright metal to serve as a reflector. A row of powerful electric lights was set in each trench. Over the top, heavy, unbreakable plate-glass was laid on a level with the surface of the ground. The pilot has only to glide down

on top of the glass in order to make a good landing. If the power-plant should break down, so that no current can be obtained for the lamps, then the flares can be used. The system betrays itself, however. The Allies fly over the illuminated aero- drome at night and drop bombs upon it. As a result, the Germans have had to use their lights only intermittently, and in some cases they had to abandon them.