The Allied submarines, like many other patrol craft, spent much of their time in those restricted waters which formed the entrances to the British Isles. Their favourite places were the English Channel, St. George's Channel, which forms the southern entrance to the Irish Sea, and the northern passage-way between Scotland and Ireland. At these points, it may be remembered, the cargo ships could usually be found sailing singly, either entirely unescorted, or escorted inadequately, while on their way to join a convoy or to their destinations after the dispersal of a convoy; these areas were thus almost the only places where the German submarines had much chance of attacking single vessels. The territory was divided into squares, each one of which was indicated by a letter: and the section assigned to each submarine was known as its "billet." Under ordinary circumstances, the Allied submarine spent all its time, while patrolling, on its own particular "billet"; only in case the pursuit of an enemy led it outside the "square" was it permissible to leave. Allied submarines also hunted the U-boats in the North Sea on the routes which the latter had to take in coming out or returning through the passages in the German mine-fields of the Heligoland Bight, or through the Skager Rack. As previously explained, in the daytime the Allied submarine remained under the water, its periscope exposed for a short time every fifteen minutes or so, sweeping the sea for a distance of many miles. As soon as darkness set in, the boat usually emerged, began taking in new air and recharging its batteries, the crew seizing the opportunity to stretch their legs and catch a welcome glimpse of the external world. The simple fact that the Allied submarines spent the larger part of their time under water, while the German spent the larger part of their time on the surface, gave our boats a great military advantage over the foe, but it likewise made existence in our submarine service more arduous. Even on the coldest winter days there could be no artificial heat, for the precious electricity could not be spared for that purpose, and the temperature inside the submarine was the temperature of the water in which it sailed. The close atmosphere, heavily laden also with the smell of oil from the engines and the odours of cooking, and the necessity of going for days at a time without a bath or even a wash, added to the discomfort. The stability of a submerged submarine is by no means perfect; the vessel is constantly rolling, and a certain number of the crew, even the experienced men, are frequently seasick. This movement sometimes made it almost impossible to stay in a bunk and sleep for any reasonable period; the poor seaman would perhaps doze off, but a lurch of the vessel would send him sprawling on the deck. One could hardly write, for it was too cold, or read, for there was little light; and because of the motion of the vessel, it was difficult to focus one's