surpass the older seats of industry in wealth and population, while the cotton export has risen to be the first in the kingdom, and the vast majority of the industrial population is now found North of the Trent. These great industrial changes were the direct consequence of the introduction of new manufacturing processes. For the use of steam power in mills necessitated the liberal use of coal, and hence the factory districts are necessarily almost coincident with the great coal-fields, as will be seen from the appended map.[47] Moreover, the coal industry had been developed almost simultaneously with the growth of manufactures, and indeed one reacted upon the other. It will be convenient here to mention the improvements made in coal-mining and in the iron trade. [47. In this industrial map it will be seen that we have (1) corresponding to the Yorks coal-field, manufactrs. of woollens, &c., cutlery, &c., lace & hosiery, machinery. (2) corresponding to the Lancs. coal-field, manufactrs. of cotton. (3) corresponding to the Staffs coal-field manufactrs. of pottery and hardware. (4) corresponding to the S. Wales coal-field smelting & iron industries.] [Illustration: MAP OF ENGLAND] § 5. THE REVOLUTION IN THE MINING INDUSTRIES--I have mentioned in a previous chapter that the development of the vast natural resources of our country as regards coal {165} and iron was retarded by the lack of steam power (p. 137). But with the steam-engines of Watt and Boulton a new era dawned upon coal-mining. In 1774 Watt, after vainly advocating his invention, entered into partnership with Matthew Boulton, a Birmingham man, and their new engine soon produced a vast change in the manner of pumping water from the mines, just as it also produced other changes in every manufacture dependent upon the use of coal. Steam power was used not only to clear the mines of water, but also in sinking shafts, where formerly entrance had often been made only by tunnelling in the side of a hill. It was used too in bringing up the coal from the pit, and in many other necessary processes. The result of this application of steam power was soon seen in the general opening up of all the English coal-fields, and the consequent further growth of towns like Newcastle, Sheffield, and Birmingham, whose industries now depend so greatly upon a large supply of coal.