20 PHYSIOGRAPHY. [chap. i. 



We shall restrict our attention, for the present, to one of 

 these river-basins of England — the basin of the Thames — 

 and endeavour to extract from its study as much instruction 

 as possible. In several of the succeeding chapters we shall 

 therefore inquire how this basin is fed with water, by what 

 means it has received its present shape, and what has been 

 its history in the past. Even the first question — how the 

 basin is fed — suggests prolific material for study. It is true 

 we have, in the present chapter, traced the Thames to its 

 head-waters, but it must not for a moment be supposed that 

 by doing this we have yet reached its real origin. The 

 streams and springs from which a river is popularly said 

 to take its rise are in truth only its proximate sources, and 

 the ultimate source is to be sought elsewhere. In seeking 

 that source, the inquiry may fitly be commenced by examin- 

 ing more closely into the nature and origin of springs. 



