The glass experiment proves to me that the jack, like all other creatures, really has a latent power of intelligence beyond that brought into play by the usual circumstances of existence. Consider the conditions under which the jack exists--the jack we have been approaching so carefully. His limits are the brook, the ponds it feeds, and the ditches that enter it. He can only move a short distance up the stream because there is a high hatch, nor can he go far down because of a mill; if he could, the conditions would be much the same; but, as a matter of fact, the space he has at his command is not much. The running water, the green flags, the lesser fishes, the water-rats, the horses and cattle on the bank--these are about all the things that he is likely to be interested in. Of these only the water, the lesser fishes, the flags, and the bottom or sides of the brook, are actually in his touch and complete understanding. As he is unable to live out of water, the horse on the bank, in whose very shadow he sometimes lies, might be a mile away for aught it concerns him. By no possible means can he discover anything about it. The horse may be itself nothing more than a shadow, unless in a shallow place he steps in and splashes. Night and day he knows, the cool night, and the sunbeams in which he basks; but he has no way of ascertaining the nature of anything outside the water. Centuries spent in such conditions could add but little to his experience. Does he hear the stream running past him? Do the particles of water, as they brush his sides and fins, cause a sound, as the wind by us? While he lurks beneath a weed in the still pool, suddenly a shoal of roach rush by with a sound like a flock of birds whose wings beat the air. The smooth surface of the still water appears to cover an utter silence, but probably to the fish there are ceaseless sounds. Water-fowl feeding in the weedy corners, whose legs depend down into the water and disturb it; water-rats diving and running along the bottom; water-beetles moving about; eels in the mud; the lower parts of flags and aquatic grasses swinging as the breeze ruffles their tips; the thud, thud of a horse's hoofs, and now and then the more distant roll of a hay-laden waggon. And thunder--how does thunder sound under the surface? It seems reasonable to suppose that fish possess a wide gamut of hearing since their other senses are necessarily somewhat curtailed, and that they are peculiarly sensitive to vibratory movements is certain from the destruction a charge of dynamite causes if exploded under water. Even in the deep sea the discharge of a torpedo will kill thousands of herrings. They are as it were killed by noise. So that there are grounds for thinking that my quiet jack in the pool, under the bank of the brook, is most keenly alive by his sense of hearing to things that are proceeding both out and in the water. More especially, no doubt, of things in the water itself. With all this