168 



KEMP'S ORE DEPOSITS. 



of the rocks. 2. Period of dolomitization of certain strata and of 

 principal ore deposition. 3. Period of dissolution of part of the 

 limestone, of breaking down of chert, and of continued but di- 

 minishing ore deposition. 4. Period of regeneration, secondary 

 deposition of carbonate of lime and quartz, and continued ore de- 

 position. 5. Period of oxidation. 



Schmidt's work was done in 1871-72. Since then the increased 



___ tuminoua 

 slate & coal 



x / . , , .. / / . .- / / / \> . , . .- , .',/,-.' f / / /'/ ,- / ' Probable flint floor of 

 f *i -J v'v'^'^V v' N/V'V'V/ <.'*.' -J \S v'v' v'v'^'v/v'' v' v \/x.'v.'v.' io'v'*' ore-deposit. 

 TYPICAL ZINC-BLENDE ORE^BODY NEAR WEBB CITY, Mo. VERTICAL SECTION, 

 ifarous Limestone 



^W^fcZmc.blende ore-bodiea 



Galenite in fissures & bedding-planes in limestone 



FIG. 43. Vertical section of a typical zincblende ore body, near Webb 

 City, Mo. After C. Henrich, M. E., June, 1892. 



development of .the mines has afforded greater opportunities for 

 observation. Haworth, in 1884, referred, with much reason, the 

 shattering of the chert in certain areas to oscillations of the strata, 

 and Clerc, in 1887, emphasized particularly the dissolving action of 

 water. A forthcoming description by W. P. Jenney, of the United 

 States Geological Survey, is awaited with great interest. While 

 the formation of the cavities and the method of introduction of 

 the ore are not so difficult to understand, it is a hard problem to 

 discover the original source of the metals. No published account 



