Pre-modern trade had many distinctive characteristics. The commodities exchanged between one region and another cannot be classified neatly into categories familiar to historians of the international economy in the age of the Industrial Revolution. The mixture of goods was much more random than was the case later. The result of the application of machinery to the production system was to create among other things an unceasing demand for raw materials and an equally compelling search for overseas markets able to absorb industrial manufactures. Large areas of the world, whole continents even, went over in the nineteenth century to the production of cereal grains, commercial crops, and minerals which were exported to the industrialised countries of the West and paid for by the import of finished consumer goods. The long-distance trade of the Indian Ocean before 1850 or 1800 obeyed a different logic. The demand for raw materials, or the transport of grains and foodstuffs, was common enough. Some of the coastal and inland areas of the Middle East, India, and China also specialised in the manufacture of industrial products. But the composition of trade between, let us say, India and China was not mainly determined by the nature of that specialisation. The factors which dominated the movement of goods in Asia's seaborne and caravan trade are not difficult to identify.