490 Horace B. Woodward — The Chalky Boulder-clay. 



That the main features of the glaciated portions of the country- 

 were carved out very much as they are now before the accumulation of 

 the Chalky Boulder-clay, is evident when we consider its distribution. 

 ]t lies in patches, or great sheets, on the Oolitic uplands, from Stow 

 Park, near Buckingham, to Lincolnshire, and on the Chalk plateaus 

 from near St. Albans to Norfolk and the Lincoln wolds; it is found also 

 in the vales beneath the escarpments, and near South Willingham, 

 in Lincolnshire, it crosses the Cretaceous scarp. Its tendency, as 

 a rule, has been to efface the old scenery, and the subsequent agents 

 of denudation have only carved out minor valleys and separated 

 the Boulder-clay into great sheets and numerous large and small 

 outlying masses. The incorporation of so much Cretaceous and 

 Jurassic material in the Boulder-clay, of course, means a great 

 amount of erosion, but this, as a rule, took place from a scouring of 

 the irregular land-surface, and was attended by a degradation rather 

 than an intensification of the main features. 



Fig. 1 . — Pit by spinny, north-west of Thorpe Limekiln, Norwich. 



2. Gravel and sand, 3 or 4 feet. Plateau Drift. 

 1. Stony loam with contorted seams and masses of sand and gravel, 

 16 feet. Contorted Drift. 



When the agent which accumulated the Boulder-clay acted with 

 greater power, the Chalk escarpment was considerably abraded, as 

 in West Norfolk, and onwards to the neighboui'hood of Stevenage 

 and Hitchin. To the south-west we find no evidence of this 

 planing down, the escarpment of the Dunstable and Luton Downs 

 is bold, and so it is continued along the further range of Chiltern 

 Hills. We do not find any Boulder-clay on the crests of these 

 higher hills. Nevertheless, we find no Boulder-clay on the crests 

 of the Lincolnshire Cliff, and this fact shows that we must be 

 cautious in inferring an absence of glaciation where no relics at 

 present exist. The presence, or absence, of loose and weathered 

 rock, and other circumstances, must here aid our conclusions. Thus, 

 in West Norfolk there is a marked absence of Clay-with-flints. 



It is admitted that ice moving over ground-moraine cannot at 

 the same locality erode. ^ Whether all the disturbances which we 



1 J. E. Dakyns, Geol. Mag. 1875, p. 169. 



