WEATHERING 



23 



water that 0.533 per cent of the entire weight of oligoclase, 1.530 

 per cent of hornblende, 0.307 per cent of magnetite, 2.018 per cent 

 of apatite, 2.111 per cent of olivine and 1.211 per cent of serpen- 

 tine were dissolved. The calcium, magnesium, and other alkalis 

 were in solution in the form of carhonates. Carbonated water acts 

 very readily upon limestone, and the caverns found in our large 

 limestone deposits in Illinois, Indiana, Kentucky, and Virginia bear 



Fio. 13. Stalactites and stalagmites formed in a cavern from limestone dissolved by 

 carbonated water while! passing through the rocks above. Hocks, Hock-Weathering 

 and Soils, Merrill. (Courtesy The Macmillan Company.) 



evidence of the great solvent power of water. Tt is stated that there 

 are 150,000 miles of subterranean passageways in the limestone 

 region of Kentucky, and practically all of this material was removed 

 by carlx>nated water. In these caves the stalactites and stalagmites 

 owe their origin to the limestone dissolved by the water l>ofore it 

 enters the cavern (Fig. 13). The solution of the limestone has 

 produced sinkholes on the surface that gives a peculiar topography 



