The spherical mine case, which contains the explosive charge and the mechanism for igniting it, is only a part of the contrivance. While at rest on board the ship this case stands upon a box-like affair, about two feet square, known as the anchor; this anchor sinks to the bottom after launching and it contains an elaborate arrangement for maintaining the mine at any desired depth beneath the surface. The bottom of the "anchor" has four wheels, on which it runs along the little railroad track on the launching deck to the jumping-off place at the stern. All along these railroad tracks the mines were stationed one back of another; as one went overboard, they would all advance a peg, a mine coming up from below on an elevator to fill up the vacant space at the end of the procession. It took a crew of hard-working, begrimed, and sweaty men to keep these mines moving and going over the stern at the regularly appointed intervals. After three or four hours had been spent in this way and the ships had started back to their base, the decks would sometimes be covered with the sleeping figures of these exhausted men. It would be impossible to speak too appreciatively of the spirit they displayed; in the whole summer there was not a single mishap of any importance. The men all felt that they were engaged in a task which had never been accomplished before, and their exhilaration increased with almost every mine that was laid. "Nails in the coffin of the Kaiser," the men called these grim instruments of vengeance. IV I have described one of these thirteen summer excursions, and the description given could be applied to all the rest. Once or twice the periscope of a submarine was sighted--without any disastrous results--but in the main this business of mine-laying was uneventful. Just what was accomplished the chart makes clear. In the summer and autumn months of 1918 the American forces laid 56,571 mines and the British 13,546. The operation was to have been a continuous one; had the war gone on for two years we should probably have laid several hundred thousand; Admiral Strauss's forces kept at the thing steadily up to the time of the armistice; they had become so expert and the barrage was producing such excellent results that we had plans nearly completed for building another at the Strait of Otranto, which would have completely closed the Adriatic Sea. Besides this undertaking the American mine-layer _Baltimore_ laid a mine-field in the North Irish Channel, the narrow waters which separate Scotland and Ireland; two German submarines which soon afterward attempted this passage were blown to pieces, and after this the mine-field was given a wide berth.