The main causes of this industrial revolution were--the application of a number of inventions and improved processes to leading industries; the incalculable advantages derived from steam power; the immense increase in the supplies of cotton, coal, minerals and other raw materials; the greater wealth of the nation, allowing of much more capital being available for industrial enterprises; and the improvement, not alone in inland communication, but in ship-building and the art of navigation, foreign markets being thus reached more readily at a time when the general political and economic conditions were especially favourable to the commercial expansion abroad which followed on our industrial expansion at home. Woollen manufactures, originally established here with the help of workers introduced from Flanders in the time of Edward III., had had a long pre-eminence, obtaining a vested interest which led to the advent of a new rival, in the form of cotton manufacturers, receiving, at first, very scanty encouragement. Woollens had made such progress that, even before the Restoration, a market was (as Dowell tells us) opened for our goods, not only in Spain, France, Italy and Germany, but also in Russia and Baltic and other ports, while they were carried by way of Archangel into Persia, and also made a market for themselves in Turkey. {187}A great part of England was turned into sheep farms for the production of wool, and by 1700 the value of woollen goods exported had risen to £3,000,000. At this time the import of raw cotton was only about 1¼ million lbs.[26] To such an extent had the woollen, and, also, the linen, industries been placed under the "protection" of the governing powers that until 1721 it was a penal offence in England to weave or sell calico--that is, a fabric consisting entirely of cotton; and down to 1774 anyone who made or sold a fabric having more than half its threads of cotton was liable to prosecution. Not until 1783 was the prohibition of British-made calicoes removed and the production in this country of all-cotton goods allowed by legislators who had been unduly solicitous of the welfare of British industry. When, in 1776, Adam Smith published his great work on "The Wealth of Nations," he certainly did state that Christopher Columbus had brought back from the New World some bales of cotton, and had shown them at the court of Spain; but he did not think it necessary to mention that a cotton industry had been started here, and was likely to contribute to the wealth of the United Kingdom.