seriously damaged, the experience was a highly disconcerting one for the crew. If a dozen depth charges were dropped, one after the other, the effect upon the men in the hunted vessel was particularly demoralizing. In the course of the war several of our own submarines were depth-charged by our own destroyers, and from our crews we obtained graphic descriptions of the sensations which resulted. It was found that men who had passed through such an ordeal were practically useless for several days, and that sometimes they were rendered permanently unfit for service. The state of nerves which followed such an experience was not unlike that new war psychosis known as shell-shock. One of our officers who had had such an adventure told me that the explosion of a single depth charge under the water might be compared to the concussion produced by the simultaneous firing of all the fourteen-inch guns of a battleship. One can only imagine what the concussion must have been when produced by ten or twenty depth charges in succession. Whether or not the submarine was destroyed or seriously injured, a depth-charged crew became extremely cautious in the future about getting anywhere in the neighbourhood of a destroyer; and among the several influences which ultimately disorganized the moral of the German U-boat service these contacts with depth charges were doubtless the most important. The hardiest under-water sailor did not care to go through such frightful moments a second time.
This statement makes it appear as though the depth charge had settled the fate of the submarine. Yet that was far from being the case, for against the ash can, with its 300 pounds of TNT, the submarine possessed one quality which gave it great defensive power. That was ability to make itself unseen. Strangely enough, the average layman is inclined to overlook this fairly apparent fact, and that is the reason why, even at the risk of repeating myself, I frequently refer to it. Indeed, the only respect in which the subsurface boat differs essentially from all other war vessels is in this power of becoming invisible. Whenever it descries danger from afar, the submarine can disappear under the water in anywhere from twenty seconds to a minute. And its great advantage is that it can detect its enemy long before
