Geological Society of London. 327 



level Boulder-clay in the neighbourhood of Liverpool, where they 

 are not smoothed and striated, are usually broken up into rubble and 

 red sand, forming a bed of variable thickness occasionally consoli- 

 dated into a breccia. This deposit he had in former papers attributed 

 to the action of land-ice. At Mowbrey brick-and-tile works, Great 

 Crosby, is a section of Keuper marls, the only one existing for 

 many miles around. The marls are overlain by Low-level Bouider- 

 clay of the usual type, and between it and the marl is a deposit from 

 3 to 4 feet thick, which at first sight is not readily distinguishable 

 from the marls, but which a careful examination of the excavations 

 from time to time as they progressed, showed to be a distinct bed. 

 In this bed, lying at all angles, were found large blocks of sandstone, 

 some of which were grooved and striated in an unmistakable manner. 

 The matrix in which they were imbedded was of the same constitu- 

 tion as the marl, and evidently formed out of it, showing in places 

 strong evidence of contortion and kneading up. The sandstone 

 blocks belonged to the Keuper formation, and some of them were 

 very similar to bands intercalated in the marls near the bottom of 

 the excavation. No erratic pebbles or boulders of any sort were 

 found in this kneaded up marl, whereas the Low-level Boulder-clay 

 is full of them. 



The author considered that the only feasible explanation of the 

 phenomenon was that the marl had been worked up into a grey clay 

 by the passage over it of land-ice, which had broken off the sand- 

 stone-bands at their outcrops, forcing the blocks into the disturbed 

 or worked-up marl. These outcrops, concealed by a mantle of 

 Low-level Boulder-clay, must be to the northward, and therefore 

 the blocks have travelled in the same direction approximately' as the 

 track of the striations on the neighbouring rocks. 



In conclusion, he contended that all the evidence points to the 

 fact before insisted upon, that the intensest period of cold preceded 

 the deposition of the Low-level Boulder-Clay, which is clearly a 

 marine deposit. 



3. "The North- Wales and Shrewsbury Coal-fields." By D. C 

 Davies, Esq., F.G.S. 



After discussing the origin of Coal-beds, and the causes of their 

 variation in structure and quality, the author proceeded to describe 

 the North Wales and Shrewsbury Coal-field, which consists of three 

 parts: — (1) The Shrewsbury field south of the Severn, exclusively 

 composed of Upper Coal-measures ; (2) the tracts north of the 

 Severn, extending from near Oswestry to north of Wrexham ; and 

 (3) the Flintshire Coal-field. The first and second are separated 

 from each other by the alluvial plain of the Severn and Vyrmoy, 

 and the second and third by the Great Bala and Yule faults. 



Some remarks on the scenery of the Welsh border-land followed, 

 and then a general section of the Carboniferous system, as developed 

 in the country described, was given, the Permian beds being included, 

 as the author considered them the upper portion of one great divi- 

 sion of Palaeozoic time. The section was as follows, with the 

 maximum thickness of each subdivision : — 



