In this demonstration the letters A, B, and C, each represent a subchaser, the central one, B, being the flagship of the division. The listener on A has picked up a noise, the direction of which is indicated by the line a a. He telephones by wireless this information to the plotting-room aboard the flagship B. The listeners on this vessel have picked up the same sound, which comes from the direction indicated by the line b b. The point at which these two lines cross is the "fix"; it shows the spot in the ocean where the submarine was stationed when the sound was first detected. The reason for having a report from the third subchaser C is merely for the purpose of corroborating the work of the other two; if three observations, made independently, agree in locating the enemy at this point, the commanding officer may safely assume that he is not chasing a will o' the wisp.

But this "fix" is merely the location of the submarine at the time when it was first heard. In the great majority of cases, however, the submerged vessel is moving; so, rapidly as the men in the plotting-room may work, the German has advanced beyond this point by the time they have finished their calculations. The subchasers, which have been drifting while these observations were being made, now start their engines at full speed, and rush up to the neighbourhood of their first "fix." Arrived there, they stop again, put over their tubes, and begin listening once more. The chances are now that the noise of the submarine is louder; the chasers are getting "warmer." It is not unlikely, however, that the direction has changed, for the submarine, which has listening devices of its own—though the German hydrophones were decidedly inferior to the American—may have heard the subchasers and may be making frantic efforts to elude them. But changing the course will help it little, for the listeners easily get the new direction, and send the details to the plotting-room, where the new "fix" is obtained in a few moments. Thus the subchasers keep inching up to their prey; at each new "fix" the noise becomes louder, until the hunters are so near that they feel justified in attacking. Putting on full speed, all three rush up to the latest "fix," drop depth charges with a lavish hand, fire the "Y" howitzers, each one of which carries two depth charges, meanwhile manning their guns on the chance that the submarine may decide to rise to the surface and give battle. In many of these hunts a destroyer accompanies the subchasers, always keeping at a considerable distance, so that the noise of its propellers will not interfere with the game; once the chasers determine the accurate "fix," they wire the position to this larger ship, which puts on full steam and dashes with the speed of an express train to the indicated spot, and adds ten or a dozen depth charges to those deposited by the chasers.

Such were the subchaser tactics in their perfection; yet it was only after much experience that the procedure began to work with clock-like regularity. At first the new world under the water proved confusing to the listeners at the tubes. This watery domain was something entirely new in human experience. When Dr. Alexander Bell invented his first telephone an attempt was made to establish a complete circuit by using the earth itself; the result was that a conglomerate of noises—moanings, shriekings, howlings, and humming sounds—came over the wire, which seemed to have become the playground of a million devils. These were the noises, hitherto unknown, which are constantly being given out by Mother Earth herself. And now it was discovered that the under-ocean, which we usually think of as a silent place, is in reality extremely vocal. The listeners at the C- and K-tubes heard many sounds in addition to the ones which they were seeking. On the K-tubes a submarine running at full speed was audible from fifteen to twenty miles, but louder noises could be heard much farther away. The day might be bright, the water quiet, and there might not be a ship anywhere within the circle of the horizon, but suddenly the listener at the tube would hear a terrific explosion, and he would know that a torpedo, perhaps forty or fifty miles distant, had blown up a merchantman, or that some merchantman had struck a mine. Again he would catch the unmistakable "chug! chug! chug!" which he learned to identify as indicating the industrious and slow progress of a convoy of twenty or thirty ships. Then a rapid humming noise would come along the wire; that was the whirling propeller of a destroyer. A faint moan caused some bewilderment at first; but it was ultimately learned that this came from a wreck, lying at the bottom, and tossed from side to side by the current; it sounded like the sigh of a ghost, and the frequency with which it was heard told how densely the floor of the ocean was covered with victims of the submarines. The larger animal life of the sea also registered itself upon the tubes. Our listeners, after a little training, could identify a whale as soon as the peculiar noise it made in swimming reached the receivers. At first a school of porpoises increased their perplexities. The "swish! swish!" which marked their progress so closely resembled the noise of a submarine that it used to lead our men astray. But practice in this game was everything; after a few trips the listener easily distinguished between the porpoise and the submarine, though the distinction was so fine that he had difficulty in telling just how he made it. In fact, our men became so expert that, out of the miscellaneous noises which overwhelmed their ears whenever the tubes were dropped into the water, they were able almost invariably to select that of the U-boat.

In many ingenious ways the chasers supplemented the work of other anti-submarine craft. Destroyers and other patrol boats kept track of the foe pretty well so long as he remained on the surface; the business of the chaser, we must remember, was to find him after he had submerged. The Commander-in-Chief on shore sometimes sent a radio that a German had appeared at an indicated spot, and disappeared beneath the waves; the chasers would then start for this location and begin hunting with their listeners. Aircraft which sighted submarines would send similar messages; convoys that had been attacked, individual ships that had been torpedoed, destroyers which had spotted their prey, only to lose track of it as soon as it submerged, would call upon the chasers to take up the battle where they had abandoned it.

As long as the chasers operated in the waters which I have indicated, those between Start Point and Lizard Head, they "got" no submarine; the explanation was simple, for as soon as the chasers and British hunting vessels became active here, the Germans abandoned this field of operations. This was the reason that the operative area of the Plymouth detachment was extended. Some of the chasers were now sent around Land's End and up the north Cornish coast, where colliers bound from Wales to France were proving tempting bait for the U-boats; others operated farther out to sea, off the Scilly Islands and west of Brest. In these regions their contacts with the submarine were quite frequent.

There was no U-boat in the German navy which the Allied forces were so ambitious to "get" as the U-53. I have already referred to this celebrated vessel and its still more celebrated commander, Captain Hans Rose. It was this submarine, it will be recalled, which had suddenly paid a ceremonious visit to Newport, R.I., in the autumn of 1916, and which, on its way back to Germany, had paused long enough off Nantucket to sink half a dozen British cargo ships. It was the same submarine which sank our own destroyer, the Jacob Jones, by a chance shot with a torpedo. Thus Americans had a peculiar reason for wishing to see it driven from the seas. About the middle of August, 1918, we discovered that the U-53 was operating in the Atlantic about 250 miles west of Brest. At the same time we learned that two German submarines were coming down the west coast of Ireland. We picked up radio messages which these three boats were exchanging; this made it quite likely that they proposed to form a junction west of Brest, and attack American transports, which were then sailing to France in great numbers. Here was an opportunity for the subchasers. The distance—250 miles to sea—would be a severe strain upon their endurance, but we assigned four hunting units, twelve boats in all, to the task, and also added to this contingent the destroyers Wilkes and Parker. On the morning of September 2nd one of these subchaser units picked up a suspicious sound. A little later the lookout on the Parker detected on the surface an object that looked like a conning-tower, with an upright just forward which seemed to be a mast and sail; as it was the favourite trick of the U-53 to disguise itself in this way, it seemed certain that the chasers were now on the track of this esteemed vessel. When this mast and sail and conning-tower suddenly disappeared under the water, these suspicions became still stronger. The Parker put on full speed, found an oilslick where the submarine had evidently been pumping its bilges, and dropped a barrage of sixteen depth charges. But had these injured the submarine? Under ordinary conditions there would have been no satisfactory answer to this question; but now three little wooden boats came up, advanced about 2,000 yards ahead of the Parker, stopped their engines, put over their tubes, and began to listen. In a few minutes they conveyed the disappointing news to the Parker that the depth charges had gone rather wild, that the submarine was still steaming ahead, and that they had obtained a "fix" of its position. But the U-53, as always, was exceedingly crafty. It knew that the chasers were on the trail; its propellers were revolving so slowly that almost no noise was made; the U-boat was stealthily trying to throw its pursuers off the scent. For two and a half hours the chasers kept up the hunt, now losing the faint noise of the U-53, now again picking it up, now turning in one direction, then abruptly in another. Late in the afternoon, however, they obtained a "fix," which disclosed the welcome fact that the submarine was only about 300 yards north of them. In a few minutes four depth charges landed on this spot.

When the waters had quieted the little craft began listening. But nothing was heard. For several days afterward the radio operators could hear German submarines calling across the void to the U-53, but there was no answer to their call. Naturally, we believed that this long-sought enemy had been destroyed; about a week later, however, our radios caught a message off the extreme northern coast of Scotland, from the U-53, telling its friends in Germany that it was on its way home. That this vessel had been seriously damaged was evident, for it had made no attacks after its experience with the subchasers; but it apparently had as many lives as a cat, for it was able, in its battered condition, to creep back to Germany around the coast of Scotland, a voyage of more than a thousand miles. The subchasers, however, at least had the satisfaction of having ended the active career of this boat. It was damaged two months before the armistice was signed, but it never recovered sufficiently from its injuries to make another voyage. Yet I must do justice to Captain Rose—he did not command the U-53 on this last voyage. It was its only trip during the whole course of the war when he had not commanded it!

The story of the U-53 ends with a touch which is characteristically German. It was one of the submarines which were surrendered to the Allies at the signing of the armistice. Its first visitors, on this occasion, were the Americans; they were eager to read its log-book, and to find out just what had happened on this final voyage. The book was on board, and it contained a record of the U-53's voyages from the day when it was commissioned up to the day when it was surrendered. Two or three pages only were missing; the Germans had ripped out that part which described the encounter with the American subchasers! They were evidently determined that we should never have the satisfaction of knowing to just what extent we had damaged the boat; this was the only revenge they could take on us.

IV

On the morning of September 6th three subchaser units, under the command of Ensign Ashley D. Adams, U.S.N.R.F., were listening at a point about 150 miles west of Land's End. At about eleven-thirty two of these units detected what was unquestionably the sound of a submarine. Moreover, the usual "fixes" disclosed that the enemy was close at hand; so close that two of the units ran up and dropped their charges. This first attack produced no result on the submarine; the depth charge from one of the howitzers, however, unfortunately landed near one of the chasers, and, though it injured no one, it put that particular unit out of commission. However, for two hours Ensign Adams's division kept closely on the heels of the quarry, now stopping to obtain a "fix," now running full speed to catch up with the fleeing prey. At one o'clock the plotting-room reported that the submerged boat was just about a hundred yards ahead. The three chasers laid barrages according to pattern, and the three "Y" guns shot their depth charges; the region of the "fix" was so generously sowed with these bombs that it seemed an impossibility that the German could have escaped.