74 PHYSIOGRAPHY. [ch. v. 



only to be removed in due course by further evaporation. 

 The waters of the earth thus move in a continued cycle, 

 without beginning and without end. From rain to river, 

 from river to sea, from sea to air, and back again from air 

 to earth — such is the circuit in which every drop of water 

 is- compelled to circulate. The observer, who, looking down 

 upon the Thames, watches the fresh water hurrying onward 

 to the sea, must remember that the sea is not its resting- 

 place, but that most of what he sees, perhaps all, will be 

 distilled afresh and return to the earth in showers which 

 may enter into the stream of Thames again ; or swell the 

 affluents of some river on the other side of the globe; or be 

 secreted for untold ages in subterranean reservoirs. In the 

 words of a wise man of old — " All the rivers run into the 

 sea ; yet the sea is not full ; unto the place from whence 

 the rivers come, thither they return again." 



