74 Feathersfonhcmgh^s Geological Report. 



general in Mexico and in Brazil. In Spix's* account of this last 

 country, it is stated that the granite hills, both on the coast and 

 in the interior, aie " covered by a pretty thick stratum of a red 

 ferruginous clay." The same deposite of red clay is found in 

 the lead-mining district of this country, near the surface of the 

 earth. Upon the occasion of my visit to the Missouri mines 

 in 1834, I was exceedingly struck with the appearances which 

 presented themselves in a gallery | upwards of one hundred 

 feet from the surface, and which was below the surface by at 

 least ninety feet of the rock formation. There the broad veins 

 of bright galena were incased in a thick wet paste of red 

 argillaceous matter, cutting with a w^axy aspect. In one of 

 the pockets, about forty feet from top to bottom, and about the 

 same width in diameter, the cavity was filled with this red 

 clay, except at the bottom, which was occupied by a large 

 plate of galena, that seemed to have sunk there by its own 

 gravity. Although some of the red soil of the metalliferous 

 districts of the Southern States may be derived from the de- 

 composition of ferruginous slates and rocks, a great portion of 

 it may have been brought to the surface from situations analo- 

 gous to those where it is found incasing the sulphuret of lead 

 in Missouri. 



In the United States both copper and iron are associated 

 with the gold, especially the last. In the gnleniferous districts, 

 the lead is found associated with zinc, and is usually confined 

 to the carboniferous limestone. Some of the metals, however, 

 which are usually found in veins, form occasionally a constit- 

 uent part of the solid rock : thus, tin is incorporated with the 

 granite in England ; and the sulphuret of lead in Missouri, at 

 Mine la Motte, is sometimes disseminated for a great extent 

 in specks through the rock, as though the stony and metallic 

 matter must necessarily have been deposited at the same time : 

 for, as I stated upon a former occasion, if either of them were 



* Vol. 1, pace 251. 



f Taplit and Perry's Mines. 



