102 Transactions. 



(5.) Deposits may be found in many regions and in inar.v 

 kinds of rocks, but mainly in mountain regions and in 

 metamorphic and igneous rocks, because the thermo- 

 sphere is nearer the surface, and ready access thereto 

 through great fissures is found mostly in these regions 

 and in these rocks. 



Professor C. R. van Hise, in a classic paper on " Some Prin- 

 ciples controlling Deposition of Ores,"* defines his views in the 

 following sentences : — 



(1.) That the greater number of ore-deposits is the result of 



the work of underground water. 

 (2.) That the material of ore-deposits is derived from rocks 



within the zone of fracture. 

 (3.) That by far the major part of the water depositing ores 



is meteoric. 

 (4.) That the flowage of water underground is caused chiefly 



by gravitative stress. 

 (5.) That the waters which perform the first work in the 



genesis of ore-deposits are descending waters. 

 (6.) Lateral secretion is therefore an essential step in the 



first concentration of ore-deposits. 

 (7.) That sulphide ores are generally deposited by ascending 



.waters in trunk channels. 

 (8.) That the majority of ore-deposits, if not all, are partly 



deposited in pre-existing openings, and are partly re- 

 placements of wall-rocks. 



It is manifest that he attaches too little importance to the 

 genetic connection existing between ore-deposits and eruptive 

 processes, and places too much dependence upon the forma rive 

 poAver of meteoric waters. 



Professor Kempf contends that mining operations in America 

 show conclusively that mines become drier with increasing 

 depth ; and deep mining in South Africa. Australia, and New 

 Zealand adds confirmation to this view. The dryness of mines 

 in depth seems to destroy the foundations of Van Hise's main 

 contention respecting the underground circulation of meteoric 

 water. 



Van Hise admits that there are ore-deposits which have a 

 direct igneous origin, but thinks they are of limited extent. In 

 his rejoinder to Kemp he somewhat modifies his former concep- 



* "The Genesis of Ore-deposits."(p. 282; also Trans. Amer. Inst. M.E., 

 Vol. XXX, 1901, p. 27. 



t J. F. Kemp, " The Role of Igneous Roeks in the Formation of Veins," 

 " The Genesis of Ore- deposits," 1901, p. 681. 



