Thus, despite the wonderful work which had been accomplished by the convoy, the Allied effort to destroy the submarine was still largely a game of blind man's buff. In our struggle against the German campaign we were deprived of one of the senses which for ages had been absolutely necessary to military operations--that of sight. We were constantly attempting to destroy an enemy whom we could not see. So far as this offensive on the water was concerned, the Allies found themselves in the position of a man who has suddenly gone blind. I make this comparison advisedly, for it at once suggests that our situation was not entirely hopeless. The man who loses the use of his eyes suffers a terrible affliction; yet this calamity does not completely destroy his usefulness. Such a person, if normally intelligent, gradually learns how to find his way around in darkness; first he slowly discovers how to move about his room; then about his house, then about his immediate neighbourhood; and ultimately he 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.