The rendering of the Aire and Calder navigable, under an Act of Parliament passed in 1699, was an important event for the then rising manufacturing towns of Leeds, Wakefield, Halifax, Bradford and Huddersfield, situate on or within a convenient distance of one or other of these two rivers which, joining at Castleford, ten miles below Leeds, thence flow in a combined stream to their junction with the Yorkshire Ouse, and so on to the Humber and the ports of Hull and Grimsby. The event in question was no less interesting because it marked a further development in an industrial transition which constitutes a leading factor in the economic history of England. The textile industries originally established in the eastern counties by refugees from the Netherlands and France afterwards spread through the southern and western counties, attaining in each district to a very considerable growth long before they were of any importance in those northern counties with which they were afterwards mainly to be associated. The migration to the north occurred at a time when the woollen industries were paramount and the cotton industries had still to attain their subsequent stupendous growth. It occurred, also, long before the Aire and the Calder were made navigable, so that, in this case, we cannot say the industrial centres already mentioned as being situated on or near to those two Yorkshire rivers were set up there, as the towns on the river {142}Severn had mainly been, in order to secure the convenience of river transport. The chief reason why the bleak and barren moorlands of the north were preferred to the fair and fertile plains of the south for the further expansion of these great national industries was that, in the days when the steam-engine of James Watt was as yet far off, the heavier rainfall in the English Highlands of the north and north-west, together with the more numerous streams pouring down mountain sides both of greater height and of greater extent than in the south, gave to the cloth-makers, not only the abundant water supply they wanted, but, also, the particular kind of motive power, through the use of water-wheels, on which they then mainly relied for the working of their machinery.