GEOLOGY OF HERTFORD SHIRK 



147 



have a lai-o-e pevcoiitage of corn, tlie diiiry-fiirms of the midland 

 counties and tho grazing- districts of the west have a large propor- 

 tion of permanent pasture. 



With this hrief account of the agricultural position, with reference 

 to England generally, of the district of which our county forms 

 a part, it will be convenient to proceed at once to a description of 

 the chief geological causes which have determined the nature of the 

 climate, soils, and agriculture of Hertfordshire. 



IT. Climate and Physical Features. 



The physical features of the surface being necessarily ruled by 

 the geological structure of the underlying rocks, we should expect, 

 from a glance at a geological map of the county, to find a great 

 sameness in the outward aspect of Hertfordshire, for, with the 

 exception of a narrow strip of Eocene strata, stretching from Eick- 

 mansworth to Bishop's Stortford, and one or two small patches of 

 Upper Greensand and Gault clay in the northern part, the whole 

 of the county lies upon the Chalk formation. The escarpment 

 formed by tlje termination of the Chalk in the north of the county 

 forms the Royston and Dunstable Downs, one of the boldest features 

 in the scenery of the county. A parallel though less-defined range of 

 hills, running along the southern borders of the county, form what 

 is known as the Tertiary escarpment, and determine the limits of 

 the outcrop of the Eocene strata previously mentioned. But, be- 

 tween these two escarpments, the undulating surface of the chalk 

 is so concealed by superficial deposits of clay, sand, and gravel, 

 that it is only on reaching the summit of the high ground, in the 

 extreme northern limits of the county, that we observe the rounded 

 downs and hollow combes so characteristic of chalk scenery. 



The geological disturbances to which the position of these two 

 escarpments is due have also determined the general slope of the 

 surface, which is, generally speaking, towards the south, the line 

 of water-parting being more or less coincident with the summit of 

 the chalk escarpment in the north of the county. This southern 

 aspect is not without an appreciable influence upon the climate, 

 and therefore upon the agricultural position of Hertfordshire; while 



