gatherings, the splendidly equipped hospitals, incidents of life in the back areas and in the trenches, and not infrequently the faces of their loved ones themselves, sun-bronzed and happy, wearing “the smile that won’t come off.” If the photographic section of the army had accomplished nothing else, its existence would have been justified a thousand times over by the service which it performed in fighting the propaganda of the Hun and in bringing cheer and comfort to the parents, wives, and sweethearts whom the boys had left behind them. * * * * * As a result of the researches and experiments which it carried on during the war, the Signal Corps has, in addition to its countless other achievements, produced several devices which are of such an astounding nature as to strain almost to the breaking-point the credulity of the layman. I am not permitting myself to indulge in the slightest exaggeration when I assert that these devices place in the hands of the United States weapons which would render this country wellnigh invulnerable in the event of our ever becoming involved in another war. But—and herein lies their greatest significance and interest—they are, beyond all question, the most important inventions, so far as their effect on the peaceful interests of the nation are concerned, which have been produced since Morse invented the telegraph, Bell perfected the telephone, and Marconi amazed us with the wireless. Imagine the value of a device which permits of a conversation being carried on between a person on the ground and an aviator in the clouds as easily as though they were seated opposite each other at a dinner-table! Such is the radiotelephone, which I have described in detail in the chapter on the Air Service but which was suggested and brought to a state of perfection by officers of the Signal Corps. Conceive, if you can, of another device which permits of nineteen separate and distinct telephone and telegraph messages being transmitted simultaneously over a single copper wire! Picture the advance in world-communication made possible by the discovery, made by General Squier, the Chief Signal Officer of the Army, that growing trees can be used as natural antennæ for both sending and receiving radio messages! And, as a climax to this amazing list of achievements, let your imagination attempt to grasp the military and commercial significance of a device for the sending over telegraph wires or cables of cipher messages which, though they can defy any system of deciphering known to science, appear in plain language at the other end! You may think, perhaps, that I am overenthusiastic; that I have used too many adjectives and exclamation-marks. But suppose that I tell you something about these inventions. Then, unless I am greatly mistaken, you will be guilty of adjectives and exclamations yourself.