These are no mere suppositions, for quite recently I heard of a case which nearly parallels the conduct of the jack. A messenger was despatched by rail to a shop for certain articles, and was desired to return by a certain time. The parcel was made up, the man took it, heard an engine whistle, turned to run, and in his haste dashed himself right through a plate-glass window into the street. He narrowly escaped decapitation, as the great pieces of glass fell like the knife of a guillotine. Cases of people injuring themselves by walking against plate-glass are by no means uncommon; when the mind is preoccupied it takes much the same place as the plate of glass in the water and the jack. Authorities on mythology state that some Oriental nations had not arrived at the conception of a fluid heaven--of free space; they thought the sky was solid, like a roof. The fish was very much in the same position. The reason why fish swim round and round in tanks, and do not beat themselves against the glass walls, is evidently because they can see where the water ends. A distinction is apparent between it and the air outside; but when the plate of glass was put inside the tank the jack saw water beyond it, or through it. I never see a fish in a tank without remembering this experiment and the long train of reflections it gives rise to. To take a fish from his native brook, and to place him suddenly in the midst of such, to him, inconceivable conditions, is almost like watching the actual creation of mind. His mind has to be created anew to meet it, and that it did ultimately meet the conditions shows that even the fish--the cold-blooded, the narrow-brained--is not confined to the grooves of hereditary knowledge alone, but is capable of wider and novel efforts. I thought the jack came out very well indeed from the trial, and I have mentioned the matter lest some should think I have attributed too much intelligence to fish. Other creatures besides fish are puzzled by glass. One day I observed a robin trying to get in at the fanlight of a hall door. Repeatedly he struck himself against it, beat it with his wings, and struggled to get through the pane. Possibly there was a spider inside which tempted him; but allowing that temptation, it was remarkable that the robin should so strive in vain. Always about houses, he must have had experience of the properties of glass, and yet forgot it so soon. His ancestors for many generations must have had experience of glass, still it did not prevent him making many trials. The slowness of the jack to learn the impenetrable nature of the glass plate and its position is not the least indication of lack of intelligence. In daily life we constantly see people do things they have observed injure them, and yet, in spite of experience, go and do the same again.