A HISTORY OF DERBYSHIRE large patch of Middle Pennine Boulder Clay. A well sunk in a brick- yard proved it to be at least 60 feet thick. It rests upon a contorted surface of Keuper Marl and skerry. The clayey matrix is composed chiefly of Coal Measure clay with varying proportions of Keuper Marl, and is wholly unstratified. Amongst the pebbles were nodules of iron- stone, Millstone Grit, chert, Coal Measure sandstone, limestone, coal and quartzites. Some of the larger erratics, one of which weighed at least 6 tons, were finely polished, striated and grooved. Another small patch of Boulder Clay caps the hill north-east of Chaddesden and north-west of Brushwood. Its junction with the upper Keuper Marl showed the stiff blue clay with boulders, contorted and crushed into the marl below, masses of the one being sometimes torn off and buried in the other. At Sheldon Wharf brickyard south of Derby, on the road to Chel- laston, was an exposure excavated in Boulder Clay. The pit was worked at two levels. The lower one showed a section of 9 or 10 feet of a loose broken red clay with pieces of Keuper Marl and pockets of sand. Small pebbles are distributed through the mass. Towards the top quartzite pebbles and fragments of carboniferous rocks begin to appear in tolerable abundance, and have their longer axes arrayed in a horizontal position. About 5 feet of silty sand and pebbles separated the redeposited red marl from the Boulder Clay above it. This clay was about 8 feet thick and contained numerous pebbles and boulders well polished and striated. The largest one seen was of carboniferous limestone and measured 20 by 1 6 inches. In addition to pebbles of quartz and quartzite were fragments of coal, ironstone, marble, chert, Coal Measure sandstone and Millstone Grit. There was no marked line of division between the beds, and Mr. Deeley considers that they were deposited in quiet water, the local rocks at the bottom, the foreign materials coming in greater abundance as the glaciers approached and deposited sand, mud and boulders in the quiet water. The deposits formed in the Trent basin during the Middle Pleisto- cene epoch indicate that important physical changes had taken place since the earlier period. These changes led to the advance of an ice sheet from a north-easterly direction, which spread out over central England the rocks it successively encountered. The abnormal direction of this ice flow probably owed its existence to a period of intense cold coupled with a considerable depression of the Pennine axis. The Boulder Clay from this ice sheet is known as the Great Chalky Boulder Clay, because of the large number of cretaceous rocks which it contains. An indication of the direction of flow was, in one instance at least, ob- tained by Mr. Teall, who found the Lias limestone south of Nottingham striated in the direction from east-north-east to west-south-west. The presence of sand below the Chalky Boulder Clay on Chellaston Hill was shown by some borings which passed through the chalky sand, then through some 40 feet of Boulder Clay into running sand, which was 6 feet deep. Under this were 10 feet of loam, sand and gravel, the 30
