Here are a couple of samples. Some readers of popular science, as it is called, may have been shocked to see in a technical journal, rather late in the war, a recklessly full description of our "listening sets"--the apparatus by which an enemy telephone message is overheard in the field. "Why," they must have thought, "this is giving away one of our subtlest devices for finding out what the enemy is about. The journal ought to be prosecuted." The article had really come from G.H.Q. It was the last thrust in a long duel. When the war opened the Germans had good apparatus for telephonic eavesdropping. We had, as usual, nothing to speak of. The most distinctly traceable result was the annihilation of our first attack at Ovillers, near Albert, early in July 1916. At the instant fixed for the attack our front at the spot was smothered under a bombardment which left us with no men to make it. A few days after when we took Ovillers, we found the piece of paper on which the man with the German "listening set" had put down, word for word, our orders for the first assault. Then we got to work. We drew our own telephones back, and we perfected our own "listening sets" till the enemy drew back his, further and further, giving up more and more of ease and rapidity of communication in order to be safe. At last a point was reached at which he had backed right out of hearing. All hope of pushing him back further still, by proving in practice that we could still overhear, was now gone. All that was left to do was to add the effects of a final bluff to the previous effects of the real strength of our hand. And so there slipped into a rather out-of-the-way English journal the indiscretion by which the reach of our electric ears was, to say the least of it, not under-stated. Few people in England might notice the article. The enemy could be trusted to do so.