92 The Ohio Journal of Science [Vol. XVII, No. 3, 



uses to which many substances can be put ; inventions which will 

 start the geologist and miner out anew. 



May we not yet find unknown sources of heat, fuel, or 

 electricity in the substances of the earth? May we not again 

 find, as we have in the past, wholly new combinations or occur- 

 rences of elements? 



Under this heading thus far I have really spoken of nothing 

 but the purely economic possibilities. From the geologic 

 side generalizations are now made on the basis of our studies 

 of the deposits mentioned above; but such generalizations and 

 any classification of ore deposits based upon them must neces- 

 sarily be subject to continual revision as new discoveries are 

 made. In some types of deposits I suppose our interpretations 

 are fairly reliable. But some of our largest salt deposits, many 

 gypsum and more anhydrite deposits are still in dispute. 

 Hundreds of deposits of sulphides, tellurides, selenides, etc., are 

 still under discussion. Whether of magmatic origin or seg- 

 regated from the sedimentary rocks in joints of which they lie, or 

 whether deposited by ascending juvenile magmatic waters, or by 

 waters once at the surface, and now, after a journey down 

 to high temperature depths, ascending with sufficient solvent 

 power to segregate the ores, is still an unsettled and, just now, 

 indeterminable question. 



In many instances the ore deposit is intimately related to 

 igneous rocks and cannot be understood until the story of 

 igneous rock genesis is written. Lindgren* says, too, that 

 "rock alteration is a subject of prime importance for the mining 

 geologist." While this subject has long been studied, but 

 little has been done in rock alterations beyond those changes 

 that make rock waste. Alterations that make rocks over, 

 andesites and limestones into highly siliceous rocks, black 

 diabases into white rocks made of calcite, quartz and micas, are 

 but little understood, and many analyses and comparisons 

 must yet be made. And conversely, because of this relation of 

 igneous rocks to ore deposits, the interpretations of the latter 

 will certainly help to elucidate the genesis of the plutonic rocks. 

 We have no right to ask to be excused from geologic research 

 until the metaliferous deposits have all been studied. How 

 long a jol) this is we cannot know, because we do not know how 



"Lindgren, W., Mineral Deposits, Page 2. 



