184 D. MACKrNTOSH ON THE DEIFT-LEPOSITS 



of a red or brown colour, with great masses of chalk imbedded and 

 partly dispersed through the clay. As some interest attaches to the 

 western boundary of what may be called the true Chalky Clay, I may 

 state that I agree with Mr. Harrison, F.G.S., in believing that it 

 does not extend further west than Charnwood forest ; and I like- 

 wise believe that for a considerable distance east of that boundary 

 the clay itself is of local derivation, and that the chalk-fragments, 

 however numerous or large, are erratics dropped into the clay 

 by floating ice. The occurrence of local, indirectly local, or erratic 

 stones in locally worked-up shale, marl, clay, &c. is a phenomenon 

 not confined to the midland counties of England. It may be seen 

 exemplified around Matlock, Belper, &c., southward across the 

 central plain of England as far, at least, as the Jurassic escarpment, 

 south-westward at least as far as Usk, Monmouthshire, and west- 

 ward along the Welsh valleys as far as St. Gleorge's Channel. 



Drift- Deposits of Leicestershire, Rutlandshire, Sfc, 



Professor Judd, in his Survey Memoir on the geology of the area 

 lying between some of the districts above noticed and Lincolnshire, 

 describes the Boulder-clay as being often underlain by sand and 

 gravel (with brick-earth), and covered by gravel-beds, which are 

 partly interstratified with the upper part of the Boulder- clay. These 

 gravel-beds consist of stones which were derived from the Boulder- 

 clay. The clay contains more and more chalk- fragments and flints 

 eastwards, until in some places it becomes almost reconstructed 

 chalk. Professor Judd in places found the clay graduating into 

 gravel on the same horizon, as if the supply of clay had become 

 exhausted while the stones continued to be carried forward. I 

 had previously noticed a similar gradual replacement of clay by 

 stones, but never fully understood it until I had read Professor 

 Judd's explanation, which ought never to be forgotten in tracing 

 Boulder-clays to greater or less distances from their sources of 

 supply. He describes enormous boulders of oolite and marlstone, 

 one of them (on Beacon Hill) being 600 feet in diameter, and refers 

 their transportation from their parent rocks to the period of the 

 glacial submergence. They are found in the lower part, as well as 

 on the surface of the Boulder-clay, This clay would appear to be 

 horizontally continuous with the great boulder-bearing clay and 

 gravel in the neighbourhood of Wolverhampton. In the British- 

 Association Boulder Beport for 1878, Mr. Molyneux, in describing 

 the boulders west of Burton- on-Trent, says: — "The boulders or 

 rock-masses occur principally at from three to ten feet below the 

 surface, intermixed with blue and yellow clay, and consist of 

 angular, subangular, and rounded fragments of Carboniferous lime- 

 stone and chert, Yoredale Sandstone, Millstone Grit, ranites [from 

 the Charnwood or Mount-Sorrel district — D. M.], porphyry, syenite, 

 greenstone," &c., " with smaller fragments of Liassic and Oolitic 

 rocks." In many parts of the eastern midland counties there is a 

 considerable thickness of gravel or sand above the horizon of the 

 clay with chalk debris. 



