SUCCESSION IX THE TRENT BASTN. 457 



thick, rests upon flinty gravel. The sand is false-bedded, and contains 

 carbonaceous seams. Brown Chalky Clay rests unconformably upon 

 it. The sand shown in a pit at Burton Lazars may also belong to 

 this age. 



On Chellaston Hill, resting upon Keiiper marl and passing 

 upwards into the Chalky Clay, there are gravelly and sandy beds of 

 an aqueous character. They are exposed in the plaster-pits on the 

 south-east side of the village. At the south end of the main cutting 

 they are well shown. 



Mr. J. W. Eardley, of Derby, has also kindly furnished me with a 

 ■description of the deposits passed through by some borings on Chel- 

 laston Hill (see fig. 3, p. 460). Two deep shafts were sunk through 

 the Chalky Sand and Chalky Clay into the sandy beds below. After 

 passing through the upper sand, and then through from 40 to 45 

 feet of Boulder-clay, the shaft entered six feet of running sand, then 

 six feet of loam, next loam and sand two feet, and then another two 

 feet of gravel which rested upon Keuper marl with gypsum. 



2. Great CTmXky Boulder-day. 



We now come to perhaps the best-known of all glacial deposits, 

 the Great Chalky Boulder- clay. 



jS'o attempt will be made to follow it out of the Trent basin, or 

 to give a detailed description of its distribution ; my intention is 

 rather to note its general mode of occurrence, its position among 

 the deposits of the Pleistocene period, and the probable method of 

 its formation. 



One of the greatest obstacles to a just appreciation of the laws 

 which regulate the formation of Boulder-clays has arisen from the 

 difficulty of determining the exact relative ages of the deposits dealt 

 with, and the idea, perhaps unconsciously adopted, that the boulders 

 they contain were always derived directly from their parent rocks. 

 For instance, the accumulation of Boulder-clays and sands encumber- 

 ing the Liassic ridge between South Nottinghamshire and Leicester- 

 shire has been regarded as belonging to one stage of the Pleistocene 

 period. In this particular area the main mass of the Chalky Clay 

 really lies to the north and east of the ridge, and has been thrust 

 against and partially over earlier Boulder-clays and sands. Indeed, 

 the presence of tolerably high land in the path of the advancing 

 glacier which moved up the Trent valley has to a great extent 

 stopped the further westerly extension of typical Chalky Clay. 

 Roughly speaking, the chalky debris was forced up the Trent valley 

 for some distance and then spread out in two long tongues — one 

 extending up the main valley as far at least as Hanbury, north- 

 west of Burton-on-Trent ; and the other over the district south of 

 the Wreak, past Leicester, and then along the southerly margin of 

 the Trent basin. How far it extends in this direction I cannot 

 say. The intermediate area of the Ashby-dc-la-Zouch coal-field 

 owes its freedom from the typical or morainic Boulder-clay of this 



