222 THE BOOK OF NATURE STUDY 



on the coalfields themselves. They are generally near their 

 borders, where the soil is better, the conditions more healthy, 

 and where good supplies of water may be obtained from springs 

 and wells which draw their water from uncontaminated sources. 

 Numerous examples will be found from the inspection of any 

 geological map, but there are few more striking instances than 

 those towns situated in rings round the Midland Coalfields. The 

 two lines of southern villages situated at the junctions of the 

 Chalk, with the Thanet Sand to the north and with the Upper 

 Greensand to the south, furnish another striking instance of the 

 attraction possessed for primitive populations of easily obtained 

 and pure supplies of water. A still more striking instance is afforded 

 by the growth of London itself. This was originally founded 

 as near the open sea as was possible before reaching the marshes 

 which occupied the mouth of the river. Here the main rock 

 Formation, the London Clay, was covered with brick earths and 

 gravels, and the latter site was naturally chosen for dwellings 

 because it both provided the water to wells and carried away the 

 drainage. The earlier growth of the twin cities of London and 

 Westminster was confined to the outcrop of the gravels, and it 

 was not till supplies of water were brought from outside that the 

 unoccupied areas of brick-earth, and finally of London Clay, were 

 taken up. Even now the chief recreation grounds, the public 

 and royal parks, represent the least desirable of the land left; 

 for they are mostly founded on London Clay or alluvial clays 

 on which building would still possess considerable disadvantages. 

 Looking over the country generally, it is found that much 

 of the land that would otherwise be waste ground on account 

 of the infertility of its soil, its imperfect drainage, or the character 

 of the rock on which it is founded, is that which is occupied by 

 commons, heath, sporting estates, and forest. Thus land which 

 would be unsuitable for residence, has little agricultural value, 

 and yields little or no industrial resources, is brought into use for 

 recreation. 



