The enemy is always listening for indications of the direction and position of gallery heads. Work must therefore be carried on with a minimum of noise. Shouting down the shafts of galleries is absolutely forbidden. When the mining operations of the enemy are detected a report should be made at once to the officer in charge of that section of the trench. CHAPTER IV Field Trenches The next element of the defensive position is the _first line fire trenches_. These are located so as to have a good field of fire to the front for several hundred yards and so constructed as to give the greatest cover and protection from the fire of the enemy. An unbroken, continuous trench would be exposed to enfilade fire. A shell, shrapnel or grenade bursting therein would have widespread effect. To overcome these elements the trench is constructed in short lengths, with traverses between them, and technically known as the _traverse type_. Better defilade is thus secured and the material effect of any burst is confined to narrow limits. The trench interval between the traverses is known as the “bay,” which should not ordinarily be longer than 18 feet. Longer bays invite heavy casualties in case the trench is enfiladed or a high explosive shell finds its mark. The illustration, Plate 14, shows a trace of the traversed type of fire trench. [Illustration: _PLAN OF TRAVERSED TYPE OF FIRE TRENCH_ _PLATE 14._ 1. Length of bay, 18 feet. 2. Width of traverse, 5 feet. 3. Length of traverse, 5 feet. 4. Overlap of traverse, 3 feet. 5. Height of traverse depends upon defilade required and practicability of concealment. ] Type of Trench Formerly, protection from the enemy’s fire was obtained by thickness of parapet. In the trench warfare of today it is obtained by completely concealing the riflemen in a deep, narrow trench with a very low parapet. The height over which the average man can fire is about 5 feet or about five-sixths of his own height. This factor determines the height of the parapet above the firing banquet of the trench or the height of bottom of loophole above the same point, when the latter is employed. The type of trench in general use today is the simple standing trench shown in Plate 15. [Illustration: PLATE 15.—Simple standing trench. 1. Width at top, 3 feet 4 inches. 2. Width at bottom, over all, 2 feet 8 inches. 3. Width of firing banquet, 1 foot 4 inches. 4. Height of parapet above firing banquet, 5 feet. 5. Height of parapet above bottom of trench, 6 feet 4 inches. ] [Illustration: _PLATE 15a._ _Type of_ _INSTRUCTION FIRE TRENCH AT VALCARTIER CANADA_ _Used in the instruction of Canadian Troops._] Drainage