This is the division of labour. It is found advantageous not only that the craftsman be employed as he is needed, but also that he produce a supply of products peculiar to his trade; for the times of labour do not in the least harmonise with the times of demand. Although during the first periods of industrial life men sought more or less to adjust these factors, in later times they become wholly separate from one another. There is always, in addition, labour ready to be expended on casual needs; in more advanced phases of civilisation this condition of affairs is not avoided; but wherever labour can be disassociated from fortuitous necessity, the capacity for production is greatly increased. Commodities are manufactured during the best seasons for production and are preserved until the times of need; thus men become independent of the moment. Here also, as in other problems of civilisation, it is necessary to surmount the incongruities of chance, and to render all circumstances serviceable to our purposes. [Sidenote: Crafts and Trades Developing] Exchange and division of labour are the great factors of the progress of a civilisation based upon industrialism. Crafts and trades develop and improve; greater and greater skill is demanded, and consequently the time of preparation necessary for the master craftsman becomes longer and longer. The worker limits himself to a definite sphere of production and carries his trade forward to a certain perfection. His wares will then be more eagerly sought for than those made by another hand; they are better, yet cheaper, for his labour is lightened by his greater skill. His various fellow craftsmen, and the agriculturist also, must exchange their goods for his; for the more specialised the work of an individual, the more necessary the community is to him, in order that he may satisfy all his various requirements. Exchange is at first natural; that is, commodities are traded outright, each individual giving goods directly in return for the goods he receives. The production of the community as a whole has become far richer, far more perfect. The labour of the organised society produces more than the activity of separate individuals. [Illustration: THE BEARERS OF MAN’S BURDENS: PRIMITIVE AND NATURAL METHODS OF CARRYING These illustrations show a palanquin borne by horses; the Chinese single-wheel cart and the same assisted by a donkey and a sail; pack mules and camels; and a sledge drawn by Esquimau dogs. ] [Illustration: SOME METHODS OF CONVEYANCE IN VARIOUS AGES AND COUNTRIES In this plate are illustrated a caravan of yaks; the elephant with a howdah; the African litter; reindeers as pack animals; and the familiar bullock waggon of France--a few of the many methods of carrying used by man. ] [Illustration: PRIMITIVE MONEY: SELLING A SLAVE FOR COWRIES