GEOLOGY OF nEllTFOUDSUIRE. 157 



althougli chalking is said to be of great advantage. But further 

 towards the east, the calcareous nature of the clay, owing to the 

 presence of chalky boulders, is so well adapted for the growth of 

 barley, that Ware malt is not excelled in any other part of the 

 kingdom. 



The character of the soil overlying the chalk district, is, in some 

 places, totally changed by the occurrence of outlying patches of 

 the Eocene beds, as at Sarratt, Abbot's Langiey, and St. Albans. 



On the whole, this drift-covered district is well separated by its 

 general arable culture, both from the hay-farming districts of the 

 south, and the sheep-farming hills in the north. Although beech- 

 trees flourish well, the oak and elm are more stunted in growth 

 than on the London-Clay soils ; but, on the whole, the district is 

 Avell-woodcd and totally different in external aspect from other 

 parts of England where the chalk is uncovered with drift. An 

 unusually fine growth of timber frequently marks the position of 

 an Eocene outlier wdiich affords a more favourable soil. 



So much has been written upon the chalk water-supply that 

 little need be said here upon that subject.* The extreme porosity 

 of the chalk renders it a most valuable reservoir for the storage of 

 "water ; and the possibility of its exhaustion, by the increasing 

 demands of the metropolis, is a question of the highest importance. 

 From an agricultural point of view, however, the main points to 

 be considered with regard to water-supply are the possibility of 

 procuring an adequate supply at moderate cost, as well as the 

 quality of the water and its suitability for irrigation purposes. It 

 is a characteristic feature of chalk districts generally to be so 

 destitute of streams that the formation can almost be traced upon a 

 map by this peculiarity alone. So much, indeed, is the scarcity of 

 ■water felt by farmers on chalk-soils, that either artificial dew- 

 ponds have to be constructed, or deep borings have to be made, at a 

 considerable expense, to below the water-level in the chalk beneath. 

 In the chalk district of Alabama even the social condition of the 

 people is influenced by this feature ; for only farmers of large 

 means can afford the deep boring necessary for successful farming. 

 But, happily, in our own county we have an abundance of streams, 

 owing to the fact that we have scarcely any bare chalk at the 

 surface. The almost universal covering of drift-deposits has com- 

 pletely changed the hydrographical features of the county ; and, 

 owing to the freqiient occurrence of gravel and sand in the beds 

 ■which rest upon the chalk, water is in many places accessible at 

 moderate depths, and our Hertfordshire farmers are relieved of 

 many of the troubles with regard to water-supply which are 

 experienced in other less-favoured chalk districts. 



In many parts of this district the streams are turned to agri- 



* See 'Trans. Watford Nat. Hist. Soc.,' Vol. I, p. 125; ' Proc. Inst. Civ. 

 Eng.,' vol. Iv, p. 252 ; Lucas, " The Chalk Water System," ' Proc. Inst. Civ. 

 Eng.,' vol. xlvii; Prestwich, ' Anniversary Address to the Geol. Soc. 1872;' 

 Evans, 'Anniversary Address to the Geol. Soc. 1876;' Clutterbuck, "Water 

 Supply," ' Joum. Eoy. Agric. Soc.,' series 2, vol. i, p. 271. 



VOL. II. — PART IV. 11 



