188 A YEAR IN SCIENCE 



cracks and crevices of rocks, it slowly but surely dis- 

 solves some of the more soluble compounds out of 

 them, and carries them in solution to some other place. 



Fig. 71. Rock has been dissolved and carried away by water 

 forming this underground channel. Water from a higher level 

 slowly passes into this channel through cracks in its walls. As 

 this water evaporates, deposits like those shown on the sides and 

 top are left. 



This is seen when the water comes to the surface again, 

 as it does in a spring, which in some instances leaves 

 a deposit of the dissolved minerals in a layer around 

 its mouth. 



The carrying power of water is an important factor 

 in producing and transporting soils. With every rain 

 some of the water "runs off" of the surface, carrying 



