Secrecy is the essence of sapping. The army does not like talking about its mines. You will never find in an official _communiqué_ anything but the vaguest indication as to the region in which “we made a sap, laid a mine, and destroyed the enemy’s position.” An important branch of sapping and mining is the listening for the sound of the enemy’s subterranean operations in special “listening galleries” running out at intervals from the main sap. A precise indication of the locality where a mine was exploded, or rather of the trench from which the shaft of the sap was sunk, might not only intimate to the enemy that our sappers and miners were active in that particular sector, but might give him valuable assistance in testing the efficacy of any special apparatus or means he employs for listening underground. As far as human foresight may judge, this book will appear before the war has reached its conclusion, and therefore I must refrain, as in the case of much else I should like to write, but may not under the eye of my friend the Censor, who will scan these pages, from enlarging on the splendid daring, the amazing resourcefulness, and the inexhaustible endurance of our sappers and miners in their subterranean galleries. I went down one of our mines one night. The proceeding was irregular, I believe, and if I had applied for permission through the official channel I make no doubt that it would have been refused. Incidentally, I was nearly shot on emerging, but that is another story. I was spending the night in our trenches, and in the course of an after-dinner stroll my host, the Captain in command of this particular section, asked me if I would care to see “our mine.” Considerations of the Censorship impel me to abridge what follows up to the moment when I found myself in a square, greasy gallery, with clay walls propped up by timber baulks leading straight out in the direction of the German trenches. Guttering candles stuck on the baulks at intervals faintly lit up as strange a scene as I have witnessed in this war.