North- Wales and Shrewsbury Coal-Fields. 73 



2. " Evidence of the Action of Land-ice at Great Crosby, Lanca- 

 shire/' By T. Mellard Eeade, Esq., E.R.S. 



The Author pointed out that the Triassic rocks under the Low- 

 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 con- 

 solidated into a breccia. This deposit he had in former papers 

 attributed to the action of land-ice. AtMowbrey 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 

 Boulder-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 constitution as the marl, and evi- 

 dently formed out of it, showing in places strong evidences 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 

 sandstone-bands at their outcrops, forcing the blocks into the dis- 

 turbed 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 tbe 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., E.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 Yyrnwy, 

 and the second and third by the G-reat 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 



