TRANSACTIONS OF THE SECTIONS. 75 



deposits in the West of England which represent that preglacial period known to 

 geologists as the Forest of Cromer period, which preceded the great general sub- 

 mergence of a large portion of Europe and the British isles beneath the waters of 

 the glacial sea. The nearly total submergence of Siluria and Wales during the 

 marine glacial period he considered as proved by the position of marine shell- 

 bearing drifts, containing large ice-worn erratics, upon mountain platforms in 

 Wales. These drifts have been found in several localities at the height of nearly 

 2000 feet above the sea. The conclusions arrived at by Sir Charles Lyell, Pro- 

 fessor Ramsay, and others, are well known, and they all tend to prove that large 

 portions of Wales and Siluria were submerged during a period of the glacial epoch, 

 which may be denominated as the glacial marine period. If this was the history 

 as regards North Wales, Mr. Symonds contended that it applies also to South 

 Wales, almost the whole of which he believes to have been submerged during this 

 glacial marine period. Accompanied by his friend, the Rev. James Hughes, he 

 had crossed the hill of Craig Turch this summer, where the river Cothi rises, half- 

 way between Llandovery and Tregarron, among the wildest scenery of South Wales. 

 Here he observed large erratic rocks resting on drift similar in position to those of 

 the Maenbras below Snowdon ; and he believed these erratics to have been trans- 

 ported from afar by ice-rafts floating over a glacial sea.* The hill platform of Craig 

 Turch, like that of Moel Tryfaen, and the Snowdon country, had been elevated, in 

 the course of ages, to its present height. In the accumulation of the marine drifts 

 of the Snowdon country there coidd be no doubt about their origin, for they con- 

 tain numerous sea-shells, and many striated, polished, erratic blocks, which must 

 have been dropped into them by floating ice. The author thinks some of the more 

 elevated mountain platform drifts of South Wales must be attributed to the same 

 origin, viz., a f/lacial marine origin; but while believing that there are unmis- 

 takeable proofs throughout Siluria of long periods of submergence and of gradual 

 elevation, as proved by the position of marine boulder-bearing drifts at different 

 elevations, the author maintained that the efl'ects of land-ice and snoiu in transport- 

 ing great masses of local rocks to long distances had not been sufficiently observed. 

 He had observed deposits of transported rocks so peculiarly local that it seemed 

 impossible to suppose they could have been left by icebergs or rafts. No geologist 

 could explore the valleys of the Wye, Severn, Usk, Towy, Tivy, Cothi, Rheidol, 

 Yswith, Teme, and Lugg, without observing that the heads of those valleys were 

 at one time filled with unstratified boulder-clay or till, and that through this till 

 the rivers have excavated their channels. This till is entirely unlike the stratified 

 boulder-bearing silts of marine origin. The boulders contained in this till are all 

 local, are frequently elevated above all signs of even the most ancient river-action, 

 have never been acted upon by water-action of any kind, and, though belonging 

 to rocks in situ in the district, have been carried across particular districts and down 

 particular hills ; wh.de as regards the erratics borne by floating icebergs they are 

 mingled and heterogeneous. On many hills in Wales you observe boidders of en- 

 tirely local origin studding hill-sides and resting on rocks to which they do not 

 belong ; but they have a local distribution, and have been derived from a local 

 centre. He had observed also that in numerous instances the transported rocks 

 never crossed a valley, as in the case of Dean Forest, where masses of millstone- 

 grit and mountain limestone are found on one side of the valley, but not one can 

 be found on the hills across the Wye. The whole tendency of Mr. Symonds's paper 

 was to show that since the elevation of the land into its present condition, glacial 

 land phenomena were continued long after that elevation, and that although there 

 are evidences of marine glacial action, those evidences have been much obliterated 

 and destroyed by the long-continued and later effect of land-ice and snow. He attri- 

 buted the transportation of the masses of subangidar gravel, which contains large 

 erratics from the Malvern range, and are distributed in patches on the Hanley and 

 Castle Morton plains, to the effect of a mass of frozen snow and ice which in former 

 days stretched from the Malverns down to the plains. The ancient river-terraces 

 of Siluria are well marked, and stand out in some instances at a height of 800 feet 

 above the existing river-channels. In Worcestershire it is difficult to make out 

 where the marine conditions ended and the river conditions commenced. 



