O NE of the outstanding features of the Industrial Revolution in Great Britain was the rapid increase in the population during the nineteenth century which doubled from 9 millions in i8o to i8 millions in I850, and again doubled itself by the end of the century. Another outstanding feature was the attractive power of industry, which drew the population from the countryside and concentrated it on the coal-fields. This process changed the whole face of the countryside, and new densely populated regions came into being in Lancashire, Yorkshire, the Scottish Lowlands, the Midlands, and parts of South Wales which before had been distinctly rural in character. At the opening of the nineteenth century the hinterland of the Port of Cardiff was already beginning to feel this attractive power of industry, but its influence was as yet relatively small and restricted to a few localities only. The two sharply divided regions of the hinterland, the one agricultural, of long standing and more or less static in character, and the other industrial, new and vigorously expanding, showed the trend of the future distribution of its population. The extent of the hinterland at that date amounted to about 504-4 square milesl and consisted of the eastern part of Glamorganshire, bounded on the east by the Rhymney River from the hamlet of Rudry to the sea; on the north by the Glamorgan-Brecknock boundary; and on the west by a line running from the Avon in a north-north-east direction to the head of the Neath Valley. The westerly and easterly margins were vague, however, since the area in the west from Bridgend to Neath overlapped with that of the natural hinterland of the Ports of Neath and Swansea, while that in the east overlapped with the natural hinterland of Newport. So scanty was the population, however, that for census purposes there were only six administrative districts, each composed of one or more civil parishes which sprawled over several valleys bearing no likeness to future urban districts. Of the total area of 504-4 square miles, the Merthyr and Aberdare districts accounted for 177 square miles, or just under 40 %, and this represented the extent of the industrial hinterland, except for isolated pockets of industry as at Llantrisant, Whitchurch and Caerphilly. At the turn of the eighteenth century, there were no more than 40,oo0 people dwelling in the whole of the hinterland and its Port, of whom a little more than one-quarter lived in the industrial districts of Merthyr and Aberdare.2 The only places which could boast of more than a thousand inhabitants were Merthyr Tydfil, Cardif, Aberdare, Llantrisant, and Coyty (near Bridgend).3 The bulk of the population outside of these small townships lived in hamlets and villages dotted over the Vale of Glamorgan