In order that the world may grow as rich as possible, each country should give its attention to producing what it can produce most easily in its present circumstances, getting other things in exchange by foreign trade. The United States can raise endless quantities of cotton, corn, bacon, meat, fruit, petroleum, besides plenty of gold, silver, copper, iron, &c. Australia, New Zealand, and South Africa will furnish much wool, hides, sugar, preserved meats, besides gold, copper, and diamonds. Tropical Africa has palm oil, ivory, teak wood, gum, &c. South America abounds in cattle from which we get tallow, hides, bones, horns, essence of beef, &c. China supplies us with vast quantities of tea, in addition to silk, ginger, and many minor commodities. India sends cotton, indigo, jute, rice, seeds, sugar, spices, and all kinds of other products. Every part of the world has some commodities which it can produce better than other countries, and if men and governments were wise, they would allow trade to be as free as possible, in order that each thing shall be produced where it costs the least labour to produce it. #23. Work in the Best Manner.# Whatever the kind of industry carried on in a place, we ought to take care, thirdly, that each labourer works in the best manner, so as not to waste his labour or to make mistakes. There are many different ways of setting about the same work, and, in order that he may choose the best, the labourer must be intelligent and skilful, or else he must be directed by some person who has knowledge and skill. Moreover, there must be, as we shall see, great division of labour, so that each man shall do the kind of work he can do best. We need, then-- (1) #Science#, (2) #Division of labour#. #24. The Need of Science.# In order that he may employ his labour to the best advantage, it is requisite that the labourer should be not merely skilful, that is, clever, and practised in handiwork, but that he should also be guided by a scientific knowledge of the things with which he is dealing. Knowledge of nature consists, to a great extent, in understanding the #causes of things#, that is, in knowing what things must be put together in order that certain other things shall be produced. Thus the steam-engine is due to the discovery that if heat be applied to water, the result is steam expanding with much force, so that a firebox, coal, boiler, and water are causes of force. Whenever we want to do any work, then, we must begin by learning, if possible, what are the causes which will produce it most easily and abundantly. By knowledge we shall often be saved from much needless labour.