The trade routes to our Atlantic coast spread out, as they approach our ports; on the other hand, the trade routes to Great Britain converge almost to a point. The far-flung steamship lanes which bring Britain her food and raw materials from half a dozen continents focus in the Irish Sea and the English Channel. To cut the communications of Great Britain, therefore, the submarines do not have to patrol two or three thousand miles of sea-coast, as would be necessary in the case of the United States; they merely need to hover around the extremely restricted waters west and south of Ireland. This was precisely the area which the Germans had selected for their main field of activity. It was here that their so-called U-boats were operating with the most deadly effect; these waters constituted their happy hunting grounds, for here came the great cargo ships, with food and supplies from America, which were bound for Liverpool and the great Channel ports. The submarines that did destruction in this region were the type that have gained universal fame as the U-boats. There were other types, which I shall describe, but the U-boats were the main reliance of the German navy; they were fairly large vessels, of about 800 tons, and carried from eight to twelve torpedoes and enough fuel and supplies to keep the sea for three or four weeks. And here let me correct one universal misapprehension. These U-boats did not have bases off the Irish and Spanish coasts, as most people still believe. Such bases would have been of no particular use to them. The cruising period of a submarine did not depend, as is the prevailing impression, upon its supply of fuel oil and food, for almost any under-water boat was able to carry enough of these essential materials for a practically indefinite period; the average U-boat, moreover, could easily make the voyage across the Atlantic and back. The cruising period depended upon its supply of torpedoes. A submarine returned to its base only after it had exhausted its supply of these destructive missiles; if it should shoot them all in twenty-four hours, then a single day would end that particular cruise; if the torpedoes lasted a month, then the submarine stayed out for that length of time. For these reasons bases on the Irish coast would have been useful only in case they could replenish the torpedoes, and this was obviously an impossibility. No, there was not the slightest mystery concerning the bases of the U-boats. When the Germans captured the city of Bruges in Belgium they transformed it into a headquarters for submarines; here many of the U-boats were assembled, and here facilities were provided for docking, repairing, and supplying them. Bruges was thus one of the main headquarters for the destructive campaign which was waged against British commerce. Bruges itself is an inland town, but from it two canals extend, one to Ostend and the other to Zeebrugge, and in this way the interior submarine base formed the