44 



its present position seems probable from its position, from the 

 absence of marks of fusion, from the appearance of the limestone 

 near the tops of the fissures where a sort of Cadmeia exists and 

 coats every projecting fragment of the rock, from similar indica- 

 tions in other lead regions where large caves are found in the lime- 

 stone, wholly incrusted with the crystallized galena, over which, 

 as it adheres to the rock, the percolation of water has caused a 

 coating of stalactite to be formed partially veiling the faces of the 

 crystals. That the sulphuret of lead may be sublimed, in the man- 

 ner just suggested, is proved by an experiment made a few years since 

 in Philadelphia, in which a mixture of lead and sulphur, in chemical 

 proportion to form galena, were placed in a well closed strong iron 

 tube, and heated for some time to a bright red heat, the upper part 

 of the tube being kept at a considerably lower temperature than 

 that in which the mixture was placed. On cooling the tube, and cut- 

 ting off the upper part, the whole material was found sublimed at 

 that part. The fossils, consisting of orthoceratites, encrinites, pro- 

 ducti and juglandites, occur in beds overlying the limestone in 

 which the lead is found. These beds are various alternations 

 of limestone and clay slate, forming a series many hundred feet 

 thick. The juglandites occur in a bed of one or two feet thick, the 

 general appearance of which is marked by ferruginous matter in 

 considerable quantities. In or near the same localities occur 

 nodules of radiated pyrites. The shells of the juglandites are some- 

 times easily separable from the nucleus ; sometimes they are wholly 

 decayed, and only the more solid nucleus remains. 



One or two of these singular fossils were found of the size of a 

 large lemon, and very strongly resembling that fruit in its exte- 

 rior figure. Marly beds of considerable thickness occur in some 

 portions of this formation, the more solid parts of which are per- 

 ceived to be composed wholly of fossils. The lead locality is 12 

 miles west of the Shamokin coal basin, at its westerly prolonga- 

 tion. 



The fossil vegetables from the coal measures of Pennsylvania 

 were from Bear Gap, 16 miles east of the Susquehanna river. 

 They consist of the usual plants accompanying both anthracite and 

 bituminous coal, and seem conclusively to prove, so far as fossils 

 may be regarded as the indices of geology, the contemporaneous- 

 ness of the anthracite and bituminous coal deposites. 



