The story of labour in this period is the story of specialization, of the separation of functions, and the evolution of classes. It is connected with the story of population, enclosures, political classes, and wage payments. While at first the accumulation of capital is the story of mines and land, and the parallel story of foreign trade, foreign wars, and foreign possessions, there then comes the application of capital to industry, firstly for the purchase of raw materials and the payment of labour, and later for the establishment of fixed capital. Just as the first story is the change from commercial to industrial capital, so the latter is that of trading capital becoming concentrated in the fixed means of production. The story of the relative shares of capital and labour in production and consumption is the story of increasingly powerful machines and increasingly mechanical workmen, accompanied by the development of economic and political classes and the slow penetration of capital downwards through them.
Though this is the general trend of economic development in the eighteenth century, the account is necessarily vague. Too many hasty generalizations have been coined about this important stage in history. As yet not one quarter of the immense amount of material which exists on the period has been completely worked, and the truth can only be obtained by working at corners of the vast mosaic. No store of information has been so neglected as the papers and documents of the firms which grew, developed, and died during the period known as the Industrial Revolution. Among such collections the papers of the firm of Boulton & Watt are important, not only as those of a typical firm, but as the record of a pioneer engineering firm which for twenty-five years was the sole source of steam power in Great Britain.