_Loadstone_, that mineral which has the mysterious power of attracting iron, and also of imparting to iron its own attractive power, was known to the Chinese before the year 121, in which year a famous Chinese dictionary was completed, wherein the word _magnet_ is defined as "the name of a stone which gives direction to a needle." This proves not only that they knew the attractive properties of the loadstone, and its power of imparting these properties to metal, but also that they were aware of the polarity of a magnetised needle. Another Chinese dictionary, published between the third and fourth centuries, speaks of ships being guided in their course to the south by means of the magnet; and in a medical work published in China in 1112, mention is made of the _variation_ of the needle, showing that the Chinese had not only used the needle as a guide at sea, but had observed this one of its well-known peculiarities--namely, the tendency of the needle to point in a _very slight degree_ away from the true north. In the thirteenth century, too, we find mention made of the needle by a poet and by two other writers; so that whatever Flavio Gioia may have done (and it is probable he did much) in the way of pushing the compass into notice in Europe, he cannot be said to be the inventor of it. That honour doubtless belongs to the Chinese. Be this as it may, the compass was invented; and in the fourteenth century it began that revolution in maritime affairs to which we have alluded. The first compasses were curiously formed. The Chinese used a magnetised needle, which they placed in a bit of rush or pith, which was floated in a basin of water, and thus allowed to move freely and turn towards the poles. They also made needles in the form of iron fish. An Arabian author of the thirteenth century thus writes:--"I heard it said that the captains in the Indian seas substitute for the needle and reed a hollow iron fish magnetised, so that, when placed in the water, it points to the north with its head and to the south with its tail. The reason that the iron fish does not sink, is that metallic bodies, even the heaviest, float when hollow and when they displace a quantity of water greater than their own weight."