The fibre of wool varies in diameter, the Saxon merino measuring 1/1370 of an inch, and the Southdown, 1/1100. Lustrous wool, it is said, should be long and strong; but if it is very fine it is not long. Strong wool may be as much as twenty inches in length. The wool of the best sheep adheres closely, and can only be removed by shearing; but there are varieties of sheep which shed their wool, as, for instance, the Persian, which drop the whole of their fleeces between January and May, when feeding on the new grass. This, then, is wool, the first use of which for cloth-making is lost in antiquity. There is no doubt that the pastoral industry is the oldest industry in the world; for even when the fruits of the earth could be eaten without tillage and without labour, the flocks and herds required care and attention. The shepherd may be regarded as the earliest pioneer of industry, as he has been for centuries the centre of fanciful romance, and the personification of far from romantic fact. The old legend of Jason and the Golden Fleece is in itself evidence of the antiquity of the knowledge of the value of wool; and much as the mythologists make out of the legend, there are some who hold that it merely is meant to record how the Greeks imported a superior kind of sheep from the Caucasus and made money thereby. Australia is now the land of the Golden Fleece, and millions of money have been made there out of the docile sheep. It is not indigenous, of course, to the land of the Southern Cross, where the only mammal known when Europeans discovered it was the kangaroo. Mr James Bonwick, a gentleman well known in Australian literature, gathered together many records of the introduction of the sheep into Australia, and of the marvellous development of the pastoral industry there in his very interesting book, _The Romance of the Wool-trade_. But, first, as to the different kinds of sheep. The Bighorn is the wild-sheep of Kamchatka, and it may be taken for granted that all species of the domestic sheep were at one time wild, or are descended from wild tribes. When the Aryan Hindus invaded India, it is recorded that they took their flocks with them; but whether the wild-sheep still to be found on the hills of Northern India are the descendants of wanderers from these flocks, or descendants of the progenitors of them, we do not pretend to say.