Welsh Journals

THE ORIGIN OF THE PHYSICAL FEATURES OF SOUTH WALES. By F. T. HOWARD, M.A., F.G.S. I. INTRODUCTION. In the early days of geology, it was customary to explain the origin of the surface features of the earth as resulting from great cataclysms. If a hill presented an uncommon outline, it was thought to be due to a volcano. The existence of a gorge was referred to an earthquake,* and of a wide valley to the Universal Deluge. But as the science of geology has become more exact, the changes of the past are explained by the changes taking place before our eyes, and the production of landscape is mainly ascribed to the slow but persistent action of rain and rivers, which themselves cause disintegration of the rock, and carry away to the sea both the products of their own destruction and those of other agents of denudation. Much, of course, depends on special circumstances. The character of the rock masses, their hardness and variability of structure and the manner in which they rest, all take part in the evolution of scenery. Theophilus Jones, in his History of Brecknockshire, writes as to the origin of the Taff Valley: This convulsion formed the present Vale of Taf, and precipitated that river into a channel at least 100 yards below; the explosion, or rather the steam arising from it, as it rent the rocks on each side, threw large fragments of them in a confused heap in the manner they appear as we begin to descend to Coed-y-Cymer, and left scattered upon the surface those immense masses of what mineralogists called plum pudding stone, slaked lime, rubbish and earth, appearing like the ruins of old castles, and lying in shapeless lumps below the upper stratum or wall of rock, and on which the action of fire is evidently discernible. Passing on to Merthyr the agitation continued taking a more southern direction, shown by the course of the river until it finally burst open the passage at Castell Coch and the opposite mountain, at one time apparently united, and here it wasted its fury."