The sense of smell is developed in the hunting dog to a degree which surpasses our imagination. How can we understand this quite ordinary fact, that the dog perceives the scent which has emanated from a hare or a partridge which has passed by the place at which he is smelling many hours previously, and is now several leagues away! The perfection of sight in the eagle and other birds of prey astonishes us equally. These birds, floating at an immense height, see their prey upon the earth, creatures much smaller than themselves, and descend upon them without deviating from the perpendicular line of their flight. The bat, accidentally deprived of sight, supplies this deficiency so well by the sense of touch, by means of his membranous wings, that he guides himself through the air, and finds his way to the interior of human dwellings, as unerringly as if he had the full use of his eyesight. To such a degree of exquisite sensibility has the sense of hearing attained among native Indian tribes, that a man, laying his ear against the earth, will detect the tread of an enemy at the distance of a league. Among musicians, also, how must the sense of hearing be cultivated by a man, who, partly by a natural gift, and partly by practice, comes to be able to detect the most minute difference in the tone of one instrument among fifty different kinds, all played at once, in an orchestra. Supposing that the senses of the superhuman being should have acquired the degree of extraordinary activity which is common to animals, and, in certain cases, to man, we can form some estimate of the power and extent of such a sensorial system.