GEOLOGY OF nERTFOUDsniRE. 153 



in it, in the form of boulders and pellets. The valleys of the Lea 

 and Miiuram are marked througliout their course by gravelly soils, 

 peat marshes, and alluvium, which form some of the lightest soils 

 in the southern portion of the county. 



llie Gault Dint rid. — This formation covers but a small portion 

 of the northern borders of the county ; but its influence is clearly 

 seen on descending the chalk ridge northwards towards Ashwcll 

 and Caldicott. Although the stilt nature of the Gault clay is here 

 masked by a thin covering of drift from the chalk hills, which are 

 in close proximity ; yet there is a marked difference between the 

 soils of this district and the light soils of the adjoining chalk hills. 

 If we compare the areas of the diiferent soils given above, we shall 

 find that, generally speaking, heavy soils predominate.*" This is 

 undoiibtedly due to the large occurrence of the chalky boulder- 

 clay in the east, to the presence of the London Clay formation in 

 the south, and to the generally heavy nature of the superficial 

 deposits covering the Chalk in the west. The greatest extent, 

 however, of heavy land is found in the northern half of the 

 county, and south of the Hitchin and Royston chalk hills. Near 

 the outcrop of the sandy beds of the Woolwich and Reading Series 

 the soils are rendered lighter in character, and a similar result is 

 also found fi'om admixture with the Mid-glacial sands and gravels, 

 which are frequently exposed beneath the boulder-clay in most of 

 the valleys on the eastern side of the county. 



In the foregoing sketch of the origin of the chief soils met with 

 in our county, there have, from necessity, been omitted many 

 mixed soils which it would be almost impossible to classify. J^o 

 clear line of demarcation can be drawn between each kind of soil ; 

 but, on the contrary, there is an insensible gradation from one into 

 the other. The characters of the soil are also in many places 

 locally modified from various causes. Thus the heavy loams of the 

 eastern boulder-clay district are frequently rendered lighter by 

 the exposure of the underlying Mid-glacial sands and gravels in 

 the lower parts of the valleys. Outlying patches of Eocene beds, 

 and various diift-deposits also, give quite a mixed character to the 

 soils of a great part of the south-western corner of the county 

 lying to the north of the Tertiary escarpment. 



The soils of Hertfordshire have been surveyed and mapped by 

 Arthur' Young,f and by G. A. Deane.J (See Plate III.) In the 

 following table an attempt is made to give a summary of these soils, 

 with the probable geological origin of each. 



* It must not, however, be imagined that the general character of Hertford- 

 shire soils is at all comparable to that of the heavy soils of Sussex. Owing to the 

 large admixture of flints, chalk-boulders, etc., many of the clays are in reality but 

 heavy loams. It is only the London-Clay district in the south which at all 

 resembles a stiff clay country. 



t See ' Report on Agriculture of Hertfordshire,' prepared for the Board of 

 Agriculture, and published in 1804. 



X See ' Improvement of Landed Estates,' by G. A. Deane. 



