388 



Passing below these layers already mentioned, we come to the 

 blue limestone. This is of different degrees of thickness, thick- 

 ening towards the west, and thinning towards the east, and con- 

 taining the fossils common to this rock. Below this is a bed of 

 baff'-colored limestone, thickening and thinning in a reverse 

 manner to the bed above. Beneath this is a sandstone from 

 forty lo one hundred feet thick, thickest on the east side ; 

 and, beneath this, the lower magnesian limestone. There are 

 still two other beds of limestone, before reaching the primary 

 rocks. 



The mounds are points which have survived a general erosion, 

 although it is generally supposed by the miners that they are the 

 result of upheaval. Upon this supposition, they have often been 

 searched for lead ore, but with no favorable result. No siliceous 

 fossils are found over this region, and if there has been erosion 

 here, this is a curious fact, as flints are found, evidently the re- 

 mains of erosion. 



At the western part of the district is an extra development of 

 the clay beds, differing entirely from any found elsewhere in the 

 district. It is a very pure pipe clay. These beds are four hundred 

 feet above the Mississippi river. At the north part, Limnese are 

 found in great numbers ; and in one spot, about six feet below 

 the surface of the ground, were found the bones of a gigantic 

 mammal, but these crumbled immediately on exposure to the air, 

 leaving a tooth only, which proved them to have belonged to the 

 fossil elephant. In a shaft, also, in this same clay, were found 

 bones, and two teeth of the Mastodon. 



Mr. Daniels next gave some account of the Mineral Veins 

 in these rocks, in the lead district. 



The veins are not found in all the surface rocks. They exist 

 principally in the gray limestone ; in this are caverns of immense 

 extent, partially or wholly filled with water, and which have been 

 penetrated to the distance of a mile or more, all containing evi- 

 dences of lead ore. The horizontal direction of the veins is, 

 generally, nearly east and west, and they are generally found in 

 groups of two or more veins, at small distances from each other. 



