After he had several times diverted himself with this experiment, he wanted to be informed of the composition of this wonderful swan. Harry therefore showed him, within the body of the bird, a large needle, which lay across it from one end to the other. In the bread with which the swan was fed, he also showed him concealed a small bar of iron. Tommy could not comprehend all this, although he saw it before his eyes; but Mr Barlow, who was present, taking up the bar of iron, and putting down several needles upon the table, Tommy was infinitely surprised to see the needles all jump up, one after another, at the approach of the bar, and shoot towards it, as if they had been possessed of life and sense. They then hung all about the bar so firmly, that, though it was lifted into the air, they all remained suspended, nor ever quitted their hold. Mr Barlow then placed a key upon the table, and putting the iron near it, the key attached itself as firmly to the bar as the needles had done before. All this appeared so surprising to Tommy, that he begged an explanation of it from Mr Barlow. That gentleman told him, "that there was a stone often found in iron mines, that was called the _loadstone_. This stone is naturally possessed of the surprising power of drawing to itself all pieces of iron that are not too large, nor placed at too great a distance. But what is equally extraordinary is, that iron itself, after having been rubbed upon the loadstone, acquires the same virtue as the stone itself, of attracting other iron. For this purpose they take small bars of iron, and rub them carefully upon the loadstone, and when they have acquired this very extraordinary power, they call them _magnets_. When Harry had seen the exhibition of the swan, upon revolving it over in his mind, he began to suspect that it was performed entirely by the power of magnetism. Upon his talking to me about the affair, I confirmed him in his opinion, and furnished him with a small magnet to put into the bread, and a large needle to conceal in the body of the bird. So this is the explanation of the feat which so much puzzled you a few days past." Mr Barlow had scarcely done speaking, when Tommy observed another curious property of the swan, which he had not found out before. This bird, when left to itself, constantly rested in one particular direction, and that direction was full north and south.