154 



J. V. ELSDEN AGEICULTTTEAL 



TABLE OF THE SOILS OF HERTFORDSHIRE. 



lY. The Intltjence of Geology upon the Ageiculttjeal Feattjees 



OF Heetfoedshiee. 



The London- Clay District. — Both from the general heavy nature 

 of the soil and from its proximity to the London markets, the 

 western part of this district is almost entirely devoted to grass- 

 farming. It has before been noticed that such a clear line of 

 division exists between the London-Clay soils and the gravelly 

 loams overlying the Chalk, that the boundary can in many 

 places be traced by the sudden termination of the grass-land 

 and hay-farms so characteristic of the north of Middlesex. The 

 characteristic trees in this part are oak, ash, and elm, with occa- 

 sional patches of fir, marking the position of a more barren, gravelly 

 soil derived from the drift. 



On reaching the Lea valley, however, a great change is observed 

 where the London Clay is covered with the fertile sandy loams 

 which form the alluvium of the Lea. 



This has been considered to be the richest tract in the whole 

 county, and from Hoddesdon to Wormley is characterised by 

 nurseries and market -gardens. The fertility of alluvium is 



