A HISTORY OF STAFFORDSHIRE and into another which swept across the Cheshire plain and finally in- vaded Staffordshire. Exactly where this great ice-sheet terminated has not been made out, but it may be roughly taken to have come to rest along a line joining Burton, Lichfield, Wolverhampton and Enville ; for north of this line the country is strewn with boulders and glacial detritus ; while to the south the relics are scanty and difficult to separate from the material spread out by the streams issuing from the foot of the ice. As the western ice approached the northern borders of the county it encountered the bold front of the North Staffordshire hills, which are only breached near Kidsgrove and to the east of Congle- ton. The ice however was of sufficient weight and thickness to override the Pottery Coalfield, and further north, in the direction of main move- ment, even reached an altitude of 1,300 feet to the east of Macclesfield. The gaps near Congleton however presented an easy overflow, and consequently we find an ice lobe penetrated down the Trent valley system, scattering its sands, clays and boulders in irregular mounds between Biddulph and Stoke-upon-Trent. To the south-east however the high ground around Cheadle almost completely arrested the further eastward course of the western ice, and consequently we meet with none or very little of its detritus between Uttoxeter and Cheadle ; on the con- trary the influence of the local Pennine glacier becomes apparent. The greatest accumulation of boulders is found on the western flanks of the North Staffordshire Coalfield and between Wolverhampton and Enville in South Staffordshire. As might be expected, they comprise a heterogeneous collection of Scotch and Lake district rocks, mingled with an occasional boulder from Wales, where the ice-sheet came into contact with the Arenig glacier. The commonest Lake district rocks are boulders of the red granite of Eskdale, granophyres from Buttermere, basalts with large crystals of augite, streaky garnetiferous lavas, amygdaloidal basalts and rhyolites. Rocks from Scotland are represented by blocks of hornblende- bearing granites and the tonalites of Galloway. The iceborne fragments are of all sizes, from mere pebbles up to blocks over 12 feet in length. Many of the larger boulders have been removed by man from their original resting-places and set up along the roadsides or at the corners of the streets in towns and villages, or in public parks, as at Wolver- hampton and Longton ; while in the western villages the streets are sometimes cobbled with the smaller stones. The boulders however represent but a small amount of the transported material. There are besides thick masses of ' Boulder Clay,' in which stones large and small lie scattered at all angles constituting in places a true ground moraine among which lenticular beds and sheets of sand are intercalated. The colour of the clay varies according to the nature of the ground swept over by the ice : it is brown or red when it lies on or has previously crossed an outcrop of Triassic rocks ; it is a deep dirty blue colour over tracts of Carboniferous rocks or in contiguous areas in advance of the ice-sheet, when it contains fragments of the Lower Carboniferous rocks, pieces of coal and even in one case portions of a coal seam, disrupted and 28
