OP THE N.W., MIDLAND, AND EASTERN COFNTIES. 187 



clay, Hessle sand, and Hessle clay of the east with the Lower blue 

 and brown Boulder-clays, Middle sand-and-gravel, and Upper 

 Boulder-clay of the north-west. In all attempts to correlate 

 these deposits, it ought not to be forgotten that the lower brown 

 clay and upper clay of the north-west maintain very much the same 

 character (irrespectively of the subjacent rocks) over extensive areas, 

 and that this is especially the case with the upper clay, which, with 

 extremely little variation, extends along certain lines continuously 

 from at least as far north as Carlisle to Berrington, south of Shrews- 

 bury (about 160 miles), and from the neighbourhood of Glossop as 

 far west at least as Menai Strait (about 100 miles) ; in other words, 

 the Upper Boulder-clay of the north-west (especially if we make 

 allowance for the great mass of it which in all probability runs 

 under the Irish Sea) covers an area equal to that of the Chalky Clay 

 of the east ; but the Chalky Clay differs very much from the upper 

 clay of the north-west in frequently varying its character with the 

 rocks on or near to which it rests, and likewise in often attaining a 

 much greater thickness than the upper clay of the north-west, which 

 is more a lurapper than a leveller of preexisting inequalities. There 

 is a bare possibility of the drift with many large boulders around 

 Wolverhampton (which, in an easterly direction, seems to graduate 

 into the Chalky Clay) being of the same age as the upper clay of the 

 north-west (which approaches at least as near to Wolverhampton as 

 Wellington) ; and if so, the upper clay of the north-west may 

 represent the Chalky Clay of the east. But three facts would appear 

 to militate against this idea : — (1) the upper clay of the north-west, 

 unlike the Wolverhampton clay, contains exceedingly few large 

 boulders*, as may be seen in the numerous and extensive excavations 

 lately made for obtaining brick-clay ; (2) the existence of exten- 

 sive gravel-beds in the east-midland counties (though not in East 

 AngHa) above a more or less chalky Boulder-clay, which are not 

 represented above the upper clay of the north-west f; (3) the 

 difference in character between the middle non-glacial sand of the 

 north-west, with no contemporaneously transported erratics (ex- 

 cepting near the mountains), and the middle glacial sand of the 

 east, with many contemporaneously transported erratics J. Some 

 time ago I corresponded for several years with Mr. S. Y. Wood, 

 P.G.S., on the subject of the correlation of the drifts of the north- 

 west and east. He then regarded the purple clay of E. Yorkshire 

 (which is horizontally continuous with the Chalky Clay of Lincoln- 

 shire) as the oldest deposit in the east with which the lower brown 



* An exception, however, to this general rule, was lately met with in the 

 Bootle-Dock excavations, near Liverpool, where many large boulders of dolerite 

 and diorite ("greenstone "), from the south of Scotland, were found. 



t It ought, however, to be recollected that, on the same principle, the theory 

 which synchronizes the Chalky Clay of the east vrith the Lower BouJder-clay of 

 the north-west would require an adequate representation of the middle glacial 

 sand of the east under the lower clay of the north-west, which is not to 

 be found. 



X See Mr. Penning's paper on the Physical Geology of East AngUa &c., Quart. 

 Journ. Geol. Soc. for May 1876. 



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