A HISTORY OF HERTFORDSHIRE 



most places where there is a large unwaterworn mass it has probably 

 been merely let down into its present position by the removal by denuda- 

 tion of the softer strata beneath it. Large boulders of this rock are 

 frequently found in our rivers, and one such was dredged up from the 

 Ver and erected on the green opposite Kingsbury, St. Albans, in 1887, 

 as the Victoria Jubilee memorial of the village of St. Michaels. 



The Reading Beds are cut into and their sands and clays are worked 

 in many of our brickfields. Good sections may be seen in the brick- 

 fields near Harefield, at Bushey, in Hatfield Park, and in others along 

 their line of outcrop. Their sands are frequently cross-bedded, indicating 

 shifting currents. They are so very variable that it is impossible to 

 construct a general section. In some places, for instance, there is a thick 

 bed of pure white sand which is altogether absent in others. 



Of the London Clay only the lower portion is represented ; the 

 basement-bed of brown sandy clay with layers of flint-pebbles, which 

 varies from about 6 to 1 2 feet in thickness, and is perhaps more truly a 

 passage-bed between the Reading Beds and the London Clay than an 

 integral member of the latter ; and a few feet of the lower portion of the 

 true London Clay. This is here a stiff clay rather brown than blue in 

 colour, appearing when freshly cut somewhat like the blue clay under 

 London when that has been exposed for some time. The London Clay 

 is usually capped on the highest points only by a pebble-gravel of Lower 

 Glacial or of pre-Glacial age, in either case the remnant of a bed of 

 gravel once of great extent. Elsewhere it is generally uncovered by 

 superficial deposits, but in the valley of the Stort it is overlaid by chalky 

 boulder-clay. Except in the valley of the Lea below Hoddesdon, where 

 there are sandy loams and low-lying peaty marshes, and also where it is 

 capped by pebble-gravel, the surface-soil upon it is a clay. 



The area over which the Eocene beds extend presents a marked 

 contrast to the Cretaceous area. Its soils, its agriculture, and its flora are 

 of an essentially Middlesex type. In the Colne and Brent districts it 

 forms grass-lands devoted to hay-farming and grazing, interspersed with 

 woods chiefly of oak, ash, elm, and fir trees ; in the Lea district, on the 

 south, owing to the rich alluvial soil, nurseries and market-gardens pre- 

 dominate ; while on the east, owing to the covering of boulder-clay, the 

 land is chiefly under arable culture, partaking of the character of the corn- 

 growing districts of the adjoining county of Essex. 



Outliers of the Eocene beds are spread over a considerable area of the 

 Upper Chalk, but there is not one to be seen beyond its limits. Most 

 of these outliers extend in an irregular line which is roughly parallel 

 with the line of outcrop of the main mass with which they have at one 

 time been continuous. As a general rule the larger outliers are towards 

 the north-east, and as they decrease in extent towards the south-west they 

 become more scattered. The largest of these outliers occupies an area 

 of 3! square miles between Braughing and Much Hadham, and consists 

 only of the Reading Beds ; the Colliers End and Sacombe outliers, of less 

 extent, follow near together, the latter of Reading Beds only, the former 



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