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I. Introduction. The Welsh rivers, of which I shall endeavour to trace the history in the following pages, flow through a hilly region composed almost wholly of Palaeozoic rocks. The greatest height is attained in the Old Red Sandstone of the Brecknock Beacons, which fall but little short of 3000 feet; but the Coal-Measures also rise into escarpments exceeding 2000 feet, and form large areas of mountain-land with an elevation of 1000 feet or more. This high ground is trenched by a series of valleys, of no great length, but important from their depth and from the fact that they penetrate a busy region, otherwise difficult of access. A watershed map of Wales presents at first sight the appearance of a meaningless mosaic, and it will be convenient to commence by dis-entangling its leading features. A main water-parting, separating the westward- from the eastward-flowing rivers, runs from the northern coast of Pembrokeshire near Fishguard, through the counties of Cardigan and Montgomery. It will be noticed that it commences with an east-and-west trend, but curves gradually northward in Central Wales, keeping near and almost parallel to the west coast. Westward from this water-parting there runs a series of short streams into the Irish Sea; eastward from it flow the Severn and the Wye, both of which traverse Wales in a south-easterly direction, but then turn south-westward to the Bristol Channel. South of the Wye we come to a group of rivers rising on subsidiary water-partings in the counties of Brecknock, Monmouth |
