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.