NOVEMBEE 22, 1901.] 



SCIENCE. 



791 



disregarded the lateral elements of the mov- 

 iag water. In many cases superimposed 

 upon the vertical movements in the fissures 

 or other openings are lateral movements, 

 as a result of which the deposits, instead of 

 being in vertical positions, are inclined, 

 often much inclined, and indeed may 

 be horizontal. Moreover, the horizontal 

 extents of the deposits may be much greater 

 than the vertical extents. Eeduced to a 

 simple and broad statement, the first con- 

 centration of many ore deposits is the work of a 

 relatively deep-water circulation, while the recon- 

 centration is the result of reactions upon an 

 earlier concentration through the agency of a rel- 

 atively shallow water circulation. Commonly 

 the deep-water circulation is lacking in free 

 oxygen and contains reducing agents, and the 

 shallow water contains free oxygen. The deep 

 water is, therefore, a reducing, and the shallow 

 water an oxidizing agent. 



In addition to the general factors already 

 considered there are many special factors 

 which have a most important, indeed, very 

 often a controlling influence in the pro- 

 duction of ore- chutes and in the localization 

 of ore in certain areas and districts. Some 

 of these factors are the complexity of open- 

 ings, the presence of impervious strata at 

 various depths, the presence of pitching 

 folds, the character of the topography. I 

 see, however, that my time is nearly gone, 

 and I shall not take up their discussion this 

 evening, but must refer those especially in- 

 terested in this phase of the subject to my 

 full paper already mentioned.* I must, 

 however, note that impervious strata are 

 frequently of controlling importance in 

 the underground circulation. Often deep 

 and shallow water circulations are sepa- 

 rated by such strata. Often also, as the re- 

 sult of the removal of impervious strata by 

 denudation, the previous deep circulation 



**Some Principles controlling the Deposition of 

 Ores,' by C. R. Van Hise, Trans. Am. Inst. Min. Eng., 

 Vol. XXX., 1901, pp. 112-146. 



ceases and the action of the shallow circu- 

 lation is inaugurated. 



At this point it may be well to briefly 

 recall the most fundamental features of the 

 water circulation which produces the ore 

 deposits. First comes the downward-mov- 

 ing, lateral-moving waters of meteoric 

 origin which take into solution metallif- 

 erous material. These waters at depth are 

 converged into trunk channels, and there, 

 while ascending, the first concentration of 

 ore deposits may result. After this first 

 concentration many of the ore deposits 

 which are worked by man have undergone 

 a later concentration, not less important 

 than the earlier, as a result of shallow de- 

 scending or lateral- moving waters. In other 

 cases, a concentration by descending, lateral- 

 moving waters alone is sufficient to explain 

 some ore deposits. It thus appears more 

 clearly than heretofore that an adequate 

 view of ore deposits must not be a descend- 

 ing-water theory, a lateral-secreting water 

 theory or an ascending- water theory alone. 

 While an individual ore deposit may be 

 produced by one of these processes, for 

 many ore deposits a satisfactory theory must be a 

 descending, lateral- secreting, ascending, descend- 

 ing, lateral- secreting theory. 



But there is no question in my mind that 

 this theory is still insufficient to fully ex- 

 plain many of the ore deposits. No knowl- 

 edge is ever complete. We move step by 

 step, carrying a theory nearer and nearer 

 completion. If, however, a theory be based 

 on good work, it usually will not prove to 

 be false ; it will be found to be incomplete. 

 Sandberger was not wrong when he said 

 lateral secretion explained many things in 

 reference to ore deposits. He was wrong 

 only when he excluded other factors. He 

 became unscientific when he carried his 

 theory further than his observations justi- 

 fied. While the theory here proposed is 

 believed to make an important advance, it 

 will sooner or later be found to be incom- 



