n8 PHYSICAL SCIENCE BK. in 



rain is ever so heavy as to wet the ground to a 

 depth of more than 10 feet. All the moisture is 

 absorbed in the upper layer of earth without getting 

 down to the lower ones. How, then, can rain, which 

 merely damps the surface, store up a supply sufficient 

 for rivers ? The greater part of it is carried off at 

 once into the sea by river-channels. But a small 

 portion is absorbed by the ground, and even that is 



2 not retained. For the ground is either dry and 

 so uses up at once the water poured into it ; or else 

 it is saturated and throws off what of the rainfall 

 it does not require. This is the reason why rivers 

 do not rise with the first rainfall ; the thirsty ground 

 absorbs it all. 



And then, again, how are we to explain the fact 

 that some rivers burst out from rocks and moun 

 tains ? What contribution can be made to them by 

 rains that are carried down over the bare crags 



3 and have no earth into which to sink ? Besides, 

 wells sunk in the very driest localities to a depth 

 of 200 or 300 feet reveal rich springs of water at 

 a depth to which rain water does not penetrate. 

 One may be sure there is no rain water there nor 

 any gathering of moisture, but living ( = spring) 

 water as it is usually called. The opinion in 

 question is disproved by this other argument, too ; 

 some springs well up in the very summit of a 

 mountain. It is plain, therefore, that the water in 

 them is forced up or forms on the spot, since all 

 the rain water runs off. 



VIII 



SOME writers think there is an exact parallelism 

 between the external and the internal distribution 



