GEOLOGY all of which were engaged in lowering the level of the country. By degrees the younger rocks were cut through, and the older revealed. A surface of very diverse stratal composition was thus laid bare, out of which, in this county, differential denudation has developed a pleasing diversity of upland and lowland. In the orientation of portions of certain of the rivers of the Wye System it is thought that there is perpetuated the direction of at least three of the original consequent streams. Mr. S. S. Buckman considers that the course of the first of these three original consequents is approximately indicated by the Wye above Hay (the ' Upper Wye '), the Monnow, the Gloucestershire Little Avon, the upper reach of the Bristol Avon, and a line connecting this with the Kennet." The second is thought to be indicated by the 'Middle Wye' (the portion between Willersley and Holme Lacy), the Gloucestershire Frome, and a line thence to Marlborough ; while the third is marked out by a portion of the Lugg (that to the north-west of Stoke Prior, near Leominster), the greater part of the Leadon, and the Churn, joining the preceding consequent somewhere near Swindon. From these remarks it will be understood that these consequents flowed across the area which is now the Lower Severn Valley. Therefore it is obvious that the valley has been hollowed out since. The theory is that it was excavated by the Severn, which — starting on a ' strongly tidal estuary,' cut its way backwards, capturing the consequents which crossed its path one after another, and diverting the waters of the rivers to the west of the ' elbow ' of capture into its own channel, and causing the beheaded streams to take their rise at some point further to the south-east. It is thought that the Middle Wye captured the head waters of the Monnow, before the Monnow was captured by a ' subsequent ' developed by the Severn ; and that this subsequent, cutting its way backwards, then captured first the Middle Wye and then the Lugg. Thus most of the drainage of the county was effected by a southerly flowing stream, and in this way the central portions of the county became hollowed out. Such in brief is this theory of river development as far as it applies to Herefordshire. It is speculative, but suggestive, and explains many otherwise unintelligible phenomena. The Superficial Deposits, etc. The deposits and various remains to be noticed in this part belong to the Pleistocene Epoch, or that epoch which intervened between the close of the Pliocene Epoch and the Roman occupation. During a part of this epoch, as is well known, the climate was very rigorous, and Arctic conditions obtained. Glaciers and ice-sheets spread over the greater part of Britain. In the north of England in particular, evidences of the Glacial Period or Great Ice Age are abundant in the form of striated rock-surfaces, boulders, and boulder-clays ; but, while in Herefordshire there are the remains of undoubted moraines, on the whole the evidence is neither so abundant nor so obvious. " Natural Science, xiv (1899), pp. 273-89. 29
