LEAD AND ZINC. 165 



2.06.04. Example 24a. Washington County, Missouri. Gash 

 veins in the Lower Magnesian limestones of eastern Missouri in 

 the same region as the disseminated ores of Example 23, and con- 

 taining galena, barite (locally called "tiff"), calcite, and residual 

 clay. The cavities are described by Whitney as resembling in all 

 respects the gash veins farther north, which, however, lie in rocks 

 higher in the geological series. These mines were the earliest 

 worked, but have been given up since the price of lead has been 

 at present figures (1875 and subsequently). The ore was obtained 

 from pockets, caves, irregular cavities, and from the overlying 

 residual clays. This whole region has been exposed and above 

 water since the close of Carboniferous times and has suffered 

 enormous surface decay (see R. Pumpelly, Tenth Census, VoL 

 XV., p. 12, and Geol. Soc. Amer., Vol. II., p. 20), which has left a 

 mantle of residual clay spread widely over its extent. In this, 

 more or less float mineral occurred. The mines were located in 

 Washington, Franklin, Jefferson, and St. Frangois counties. 1 



2.06.05. Example 24b. Livingston County, Kentucky. Veins 

 in limestone of the St. Louis stage of the Lower Carboniferous, 

 containing galena in a gangue of fluorite, calcite, and clay. The 



James Hall, "Notes on the Geology of the Western States," Amer. Jour. 

 Sci., i., XLII. 51. J. T. Hodge, " On the Wisconsin and Missouri Lead Re- 

 gion," Amer. Jour. Sci., i., XLIII. 35. R. D. Irving, "Mineral Resources 

 of Wisconsin," M. E., VIII. 478. E. James, " Remarks on the Limestones 

 of the Mississippi Valley Lead Mines," Phil. Acad. Sci., V., Part I., p. 51. 

 J. Murrish, Report on the lead regions, 1871, as commissioner for their 

 survey. D. D. Owen, "Report on the Lead Region," U. S. Senate Docu- 

 ments, 1844. J. G. Percival, Wis. Geol. Survey, 1856. Squier and Davis, 

 Historical account, Smithsonian Contributions, Vol. I., p. 208. M. Strong, 

 Wis. Geol. Survey, 1877, I. 637;" II. 645, 689. J, D. Whitney, Wis. Geol. 

 Survey, 1861-62, 1. 221. Rec. Metallic Wealth, p. 403, 1856. " On the Oc- 

 currence of Bones and Teeth in the Lead-bearing Crevices," A. A. A. S., 

 1859. 



ILLINOIS. 



J. Shaw, Geol. Survey of Illinois, 1873, Vol. II., p. 340. J. D. Whit- 

 ney, Geol. Survey of Illinois, 1866, Vol. I. 153. 



IOWA. 



C. A. White, Iowa Geol. Survey, 1870, Vol. II., p. 339. J. D. Whit- 

 ney, Iowa Geol. Survey, 1858, Vol. L, p. 422. 



1 Compare the older references under Example 23, and the following: 

 A. Litton, Second Ann. Rep. Missouri Geol. Survey, 1854. J. D. Whitney, 

 Metallic Wealth, p. 419. 



