328 SECTIONAL TRANSACTIONS.— C. 



fractures are related to areas of heavy sedimentation in Carboniferous times. A saddle- 

 shaped structure was produced and the thin cover of Carboniferous rocks on the 

 rigid sub-stratum was wrinkled into low ' plis de couverture ' — the Cotherstone and 

 Middleton Folds. Relation of this movement to Whin Sill intrusion. The fault block, 

 formed early, acted as a horst to the folds produced in the Pendle trough. Relation 

 ©f these movements to the deposition of Permo-Trias east and west of Pennines. 



Afternoon. 

 Excursion to the Permian Rocks of Harrogate and Knaresborough. 



Wednesday, September 7. 



Dr. A. R. Dwerryhouse and Mr. A. Austin Miller. — The Glaciation of 

 Radnorshire and Parts of the Adjoining Counties. 



We wish to place on record some preliminary observations on the district ajid to 

 indicate the general conclusions at which we have arrived. 



The work is being undertaken with the aid of a grant from the Research Board of 

 the University of Reading. 



Certain anomalies in the drainage of the country lying to the east of Clun Forest 

 and Radnor Forest first attracted our attention, and it early became evident that the 

 peculiarities were due to the action of ice during the Glacial Period. 



The main facts as we see them at present are as follows : — 



1. The country lying immediately to the west of Clun Forest, Radnor Forest, and 

 the range of hills extending southwards from the latter to the gorge of the Wye near 

 Builth Wells, was occupied by ice which was continuous with that of the Plmlimon 

 Highlands and which was moving in a southerly direction down the valleys of the 

 Ithon and Wye, and thence by way of Llanwrhyd Wells and Llandovery towards 

 Llandeilo. 



2. This ice rose to considerable heights on the western flanks of Radnor Forest 

 and penetrated to some of the valleys on its eastern side. 



3. A series of small lakes and Mawn (Peat) Pools mark the limit of this western 

 ice at a stage during its retreat. They occur at heights varying from 1,250 to 1,600 feet 

 from the latitude of Newtown (Montgomery) to that of Builth Wells in the south. 



4. Much ice passed eastwards over the area of the Wye gorge and the valley of the 

 Arrow, fanning out when it reached the more open country on the east side of the 

 range. 



5. A lobe of this glacier passed north-eastwards past Leominster, laying down a 

 terminal moraine at Orleton, causing the easterly deflection of the River Teme past 

 Tenbury. 



G. The River Lugg and its tributaries were also diverted, several lakes and overflow 

 channels resulting from the damming up of their waters by the ice. Of the overflows 

 the Downton gorge and the valleys in the neighbourhood of Mortimer's Cross may be 

 cited as examples, while the lakes which formerly existed at Presteign and in the Vale 

 of Wigmore are typical of the latter. 



We acknowledge much valuable information contained in the papers by the Rev. 

 E. Grindley and others published in the Proceedings of the Woolhope Club. 



Dr. A. Raistrick.— Periodicity in the Glacial Retreat in West Yorkshire. 



In the valleys of the rivers Aire, Wharfe, Nidd, Vre, and Swale, of West Yorkshire, 

 the earlier stages of the glacial retreat are marked by lakes impounded in the 

 tributary valleys, and a very complex system of overflow channels cut by the lake 

 waters over the lateral spurs of the valleys, sometimes accompanied by lateral moraines 

 on the main valley slopes. These lakes and channels belong to two main periods of 

 retreat, separated by a short period of readvance of the ice. A third stage of the main 

 retreat is marked by numerous terminal moraines left on the main valley floors by the 

 rapidly retreating and dwindling ice tongues of the valley glaciers. This retreat was 

 frequently interrupted by brief periods of moraine formation, and it has been found 

 that six principal pauses, with corresponding moraine belts, can be recognised, and the 

 moraines are practically complete, in all five vallevs. Most of the moraines were 



