Often dugouts are but shelters dug into the wall of a trench, a thin sheet-iron roof put on top, and two or three layers of sandbags on top of that. This gives protection against bullets, shrapnel, or bits of shell, but a straight hit from a medium-sized shell would go right through. And yet it is strange how seldom these are hit direct, considering their large numbers. This may in part account for one's feeling of relative security while in them, but this feeling is no doubt also partly due to our resemblance to the ostrich which hides its head to avoid danger. Be this as it may, many a good night's sleep have I passed in shelters such as this, with shells bursting within one hundred yards at frequent intervals during the night. During the month previous to the Battle of Arras my orderlies and I lived in an abode of this nature most of the time, only 500 yards from our front line trenches. Shells continually fell well within the hundred yard radius of it--as a matter of fact, shortly afterwards this dugout was completely blown in--yet no one worried in the least about it. This is not told as a strange experience, for all officers who have served at the front have often lived in the same surroundings. This experience is related only to illustrate one type of protective shelter. Deep dugouts vary in depth anywhere from ten to forty or fifty feet in cases where the soldier has had to do all the digging, but in some cases where limestone quarrying has been extensively carried on there have often been found, ready to hand, caves, sixty to one hundred feet in depth, such as the famous Zivy cave, opposite Mt. St. Eloy. There are many of them about this region, some of which, as the one mentioned, are large enough to give shelter to 1000 men. Usually there is a circular airshaft in the center. This shaft in Zivy cave was the target for months for German gunners, as they had occupied this region, and knew it well. In fact the story is told that in this cave, or one of the others near about, 800 Germans were gassed and killed by the French when they retook this ground. How much truth is in the story it is difficult to say. But at any rate, all through the hard, cold winter of 1916-17 the Canadians who were holding this front found good protection and some warmth in this cave for many of their men, though at all times the air in it had a grayish tinge, as the ventilation was hardly up-to-date.