Miss Eyton — Age of the Western Counties Cla'g. 545 



II. — On the Age and GEOLOCficAL Position of the Bj-ue Clay 



OF TUB Western Counties. 



By Miss Charlotte Eyton. 



IT is a well-known fact that the shell -bearing gravels of the 

 Western counties repose in many localities immediately upon a 

 bed of blue or grey clay. This bed has been described as it appears in 

 Lancashire and Cheshire, by Mr. Binney^; and more recently by 

 Professor HulP ; in ISTorth Wales by Mr. E. D. Darbishire^ ; 

 near Eugby by Mr. Wilson^ ; and in numerous localities by Messrs. 

 Taylor, H. F. Hall, D. Mackintosh, and other contributors to the 

 Geological Magazine, in various papers, all testifying to the great 

 extent and importance of this bed. 



A line drawn from north-west to south-east, from the Menai 

 Straits, passing through Shrewsbury and Coal-brook-dale, and a 

 little to the south of Eugby, will give a probable approximation to 

 the southernr boundary of this clay. On the west it extends into the 

 bed of the Irish Channel, but does not attain to any great thickness 

 among the Welsh mountains, though in the neighbourhood of 

 Llandudno Mr. Hall assigns to it the unusual depth of 150ft.^ 



It appears to arrive at its greatest importance in the level plain of 

 North Shropshire, Cheshire, and Lancashire, where it varies from 

 about 25ft. to lOOft. thick. In Shropshire and in the neighbourhood 

 of Crewe it is a stiff pure clay, free from silt, and with but few 

 included fragments, and, very rarely, shells. It has, in fact, all the 

 character of a deep-sea deposit. On the east of the plain it thins 

 out, leaving the shell-bearing gravels in the neighbourhood of the 

 Wrekin, to repose immediately upon the rock or upon the intercalated 

 beds of red sand and mud which occur at "all levels, being derived 

 from the Eed Sandstone of the locality. The same is the case in 

 Cheshire, where the blue clay is found in its fullest development 

 round Crewe, but disappears beneath the sandy gravels which, on 

 the west of Congleton Edge, and above Macclesfield, repose directly 

 upon the grit. Isolated patches, however, occur at high levels 

 further east. One of these is seen near Swithamley Park, the seat 

 of — Brocklehurst, Esq. ; and in the lower part of the Biddulph 

 synclinal, east of Congleton Edge, there is a small bed of impure clay, 

 the constituents of which seem to be chiefly blue clay largely mixed 

 with sand of various colours derived from the local grits. 



The most southern point at which I know this bed to occur in 

 Shropshire is a clay -pit near Leaton, between four and five miles 

 west of Shrewsbury. It is highly probable, however, that it forms 

 the base of Strethill, Coal-brook-dale. 



In sinking a well at the Old Woods clay -pit, about a mile from 

 the former locality, a bed of fine gravel, containing round quartz 

 pebbles, flints, and granite, was found under 25 feet of clay. The 



^ Papers read before the Manchester Geological Society, 1842, 



^ Glacial Phenomena of Western Lancashire and Cheshire. 



3 Memoirs of the Literary and Philosophic Society of Manchester, 18'68. 



* Eeport of the Rugby School Natural History Society, 1869. 



* Geological Magazine, Nov. 1870. 



