No ship is off the line by so much as a quarter length. Commander Canaga stands with watch in hand—“two minutes, one minute, thirty seconds, fifteen?” He looks up inquiringly. A nod—all right. “Five seconds—haul down!” Up go the red flags on the first ships to plant, the sign that their minelaying has begun, and word comes from the flagship’s launching station at the stern, “First mine over.” All well so far. The minelaying now runs entirely by the time table. Each ship gives her successor five minutes warning and, as her last mine dives overboard, shows the signal “Begin minelaying at once; I have suspended.” The successor begins accordingly, showing her red flag. The staff officers on board the _San Francisco_ watch for these signals, comparing the times with what they should be, and counting also the seconds elapsed between the launching of successive mines, from the ships whose sterns we can see. A few seconds out now and then—otherwise all goes according to schedule, just as planned before leaving the United States. The hardest task is on board the _Housatonic_—a new ship, with a new mining installation, of type untried in service, and a crew inexperienced in minelaying—dropping 675 mines without intermission, 1 every 11½ seconds, during 2 hours and 10 minutes. Her mate is standing by, ready for any interruption, but the _Housatonic_ completes the task without a break—making a world record, a continuous line of mines, 28 miles long. On a later occasion, the _Canonicus_ planted 860 mines in 3 hours 35 minutes, an unbroken line of 43 miles. About 20 minutes after planting began, an explosion was felt and a geyser seen astern. A few minutes later the same occurred again, and other explosions followed, at varying intervals and distances, some just visible on the horizon. Others which were nearer, as evidenced by the sharpness of the shock, threw up no geyser, indicating that they were at the middle or lowest depth. In the proof tests held off Cape Ann in April, it had been observed that a mine at the middle level, 160 feet submergence, made no surface disturbance when detonated, until 8 seconds had elapsed, and then only as much as the wash of a light swell over a submerged rock. At the deepest level, 240 feet submergence, a detonation produced no more surface upheaval than there is in a glass of well iced champagne. The ship being about 800 yards away, the shock was heavy and sharp. The water surface all over could be seen to tremble with the shock, but directly over the mine itself, when, after 27 seconds, the gas came up, there was no more surface disturbance than a pleasure canoe could have ridden with safety. A slick on the water would follow, but this could not be distinguished at much over a mile distance nor at all if there were a white cap sea running.