REVIEWS 



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by circulating waters that have come up from below, down from above, 

 or in from the sides, it being immaterial from which direction. 



Of recent years there has been a growing tendency for the large 

 mining companies to pay more attention to the geological features of 

 their properties, and in many cases a regularly trairTed geologist has 

 been employed. Dr. Keyes emphasizes this fact when he says that 

 "When a specially trained geologist undertakes to make an investiga- 

 tion of a mining property, he first gets his bearings, as it were, with 

 regard to the geological structure of the region and the distribution of 

 the rock formations. At once he eliminates nine tenths of the chances 

 of failure in arriving at the best plan for practical operation. Instead 

 of a great game of chance, the development becomes a strictly business 

 proposition." 



After briefly discussing the nature of ore deposits, the general 

 methods of ore formation, and the character of the literature, the cri- 

 teria for ore classification are formulated. The following table sums 

 up the proposed scheme : 



CLASSIFICATION OF ORE DEPOSITS. 



