fore 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.
Tommy inquired the reason of this, and Mr Barlow gave him this additional explanation: "The persons who first discovered the wonderful powers of the loadstone, in communicating its virtues to iron, diverted themselves, as we do now, in touching needles and small pieces of iron, which they made to float upon water, and attracted them about with other pieces of iron. But it was not long before they found out, as you do now, another surprising property of this wonderful stone; they observed, that when a needle had once been touched by the loadstone, if it was left to float upon the water without restraint, it would invariably turn itself towards the north. In a short time they improved the discovery farther, and contrived to suspend the middle of the needle upon a point, so loosely that it could move about in every direction; this they covered with a glass case, and by this means they always had it in their power to find out all the quarters of the heavens and earth."
Tommy.—Was this discovery of any great use?
Mr Barlow.—Before this time they had no other method of finding their way along the sea, but by observing the stars. They knew, by experience, in what part of the sky certain stars appeared at every season of the year, and this enabled them to discover east, west, north, and south. But when they set out from their own country by sea, they knew in which direction the place was situated which they were going to. If it lay to the east, they had only to keep the head of the ship turned full to that quarter of the heavens, and they would arrive at the place they were going to; and this they were enabled to do by observing the stars. But frequently the weather was thick, and the stars no longer appeared, and then they were left to wander about the pathless ocean without the smallest track to guide them in their course.
Tommy.—Poor people! they must be in a dreadful situation indeed, tossed about on such an immense place as the sea, in the middle of a dark night, and not able even to guess at their situation.
Mr Barlow.—For this reason they seldom dared to venture out of sight of the shore, for fear of losing their way, by which means all their voyages were long and tedious; for they were obliged to make them several times as long as they would have done, could they have taken the straight and nearest way. But soon after the discovery of this admirable property of the loadstone, they found that the needle, which had been thus prepared, was capable of showing them the different points of the heavens, even in the darkest night. This enabled them to sail with
greater security, and to venture boldly upon the immense ocean, which they had always feared before.
Tommy.—How extraordinary that a little stone should enable people to cross the sea, and to find their way from one country to another! But I wonder why they take all these pains.