GEOLOGY. 247 



render it doubtful. As this formation occupies but a small 

 corner of the district, the examinations were necessarily too 

 limited to enable me to pronounce, Avith confidence, upon its 

 lead-bearing character. 



" All the valuable deposits of lead ore which have as yet 

 been discovered, occur either in fissures or rents in the cliff 

 rock, or else are found imbedded in the recent deposits which 

 overlie these rocks. These fissures vary from the thickness 

 of a wafer to thirty or even fifty feet in thickness ; and many 

 of them extend to a very great, and at present unknown 

 depth. 



" The most common diameter of fissures filled with solid 

 ore is from one to four inches. 



" In the Apple river diggings, one vein filled up with ore 

 was reported to me as being, w^here then worked, four feet 

 across ; but an experienced miner, living close to the Illinois 

 line, in one of the richest spots in the district, informed me 

 that he had never seen a solid vein continue, for any conside- 

 rable distance, of greater thickness than one foot. 



" In the spring of 1828 there was a mass of lead ore found 

 in an east-and-west crevice, at the Vinegar-hill diggings, about 

 thkty-five feet in length, expanding in the centre to the width 

 of six or eight feet, and terminating in a point at each end. 

 It was a holloAV, and its walls averaged about a foot in thick- 

 ness, forming, as it were, a huge shell of mineral. This ex- 

 traordinary natural chamber was cleared out ; a table spread 

 within it on the 4th of July ; and a considerable company 

 celebrated the national anniversary within its leaden walls, 

 about sixty feet below the surface of the earth. 



" The formation of caverns, by the occasional expansion 

 of the lead-bearing crevice to a considerable width and height, 

 is not uncommon. The ceiHng of such a subterranean cham- 

 ber is commonly adorned with large, pendant, icicle-like sta- 



