Page:Victory at Sea - William Sowden Sims and Burton J. Hendrick.djvu/188

170 becomes so expert that he can be trusted to walk alone in crowded streets, to pilot himself up and down strange buildings, and even to go on long journeys. In time he learns to read, to play cards and chess, and not infrequently even to resume his old profession or occupation; indeed his existence, despite the deprivation of what many regard as the most indispensable of the senses, becomes again practically a normal process. His whole experience, of course, is one of the most beautiful demonstrations we have of the exquisite economy of Nature. What has happened in the case of this stricken man is that his other senses have come to fill the place of the one which he has lost. Deprived of sight, he is forced to form his contacts with the external world by using his other senses, especially those of touch and hearing. So long as he could see clearly these senses had lain half developed; he had never used them to any extent that remotely approached their full powers ; but now that they are called into constant action they gradually increase in strength to a degree that seems abnormal, precisely as a disused muscle, when regularly exercised, acquires a hitherto unsuspected vigour.

This illustration applies to the predicament in which the Allied navies now found themselves. When they attempted to fight the submarine they discovered that they had gone hopelessly blind. Like the sightless man, however, they still had other senses left; and it remained for them to develop these to take the place of the one of which they had been deprived. The faculty which it seemed most likely that they could increase by stimulation was that of hearing. Our men could not detect the presence of the submarine with their eyes; could they not do so with their ears ? Their enemy could make himself unseen at will, but he could not make himself unheard, except by stopping his motors. In fact, when the submarine was under water the vibrations, due to the peculiar shape of its propellers and hull, and to its electric motors, produced sound waves that resembled nothing else in art or nature. It now clearly became the business of naval science to take advantage of this phenomenon to track the submarine after it had submerged. Once this feat had been accomplished, the only advantage which the under-water boat possessed over other warcraft, that