420 



EDWARD STEIDTMANN 



of the limestones and sandstones undoubtedly contain much 

 more calcium than magnesium, although no estimate of their rela- 

 tive proportions can be given. Since the ratio of calcium to mag- 

 nesium in the average sandstone (Clarke's) is 5 . 50 to 1, it is prob- 

 able that the ratio of calcium to magnesium of the cementing 

 materials in the sandstones is even higher. 



The solutions which percolate through shales, clays, and other 

 silicates are known to suffer an exchange of bases and other 

 changes through the interaction of water solutions and silicates. 

 This interaction is dependent upon the condition of chemical 

 equilibrium between the solutions and the silicates. Kiilenberg 1 

 and other experimenters have shown that soils absorb more potassa 

 and magnesia than lime and soda. The great absorption of 

 potassa by soils and the very slight absorption of soda has been 

 interpreted as the reason why land plants utilize potassa more 

 largely than soda. 



TABLE XXVI 



Ratio of Calcium to Magnesium in the Chloride Waters of the Deep Copper 

 Mines of Michigan, as Compared with the Surface Water 



The influence of silicates in the belt of cementation on the 

 calcium magnesium ratio of underground waters is suggested by 

 a comparison of the calcium magnesium ratio of the surface and 

 deep waters of the copper mines of Lake Superior. The deep 

 waters are probably the modified residuum left from the cycle 

 of deposition which developed the ores and gangue minerals. 

 The result of cementing processes has been a concentration of 

 calcium in the solutions. Magnesium has evidently been forced 

 out of solution by the conditions of chemical equilibrium. See 

 Table XXVI. 



1 Mitteil. d. Landw. Centrahereins fur Schlesien, Heft 15, p. 83, quoted by E. C. 

 Sullivan, Bull. 312, U.S.G.S., 16-19. 



