24 EXPEDITION TO THE 



quality ; but in this manner a safer roof is obtained for the 

 excavation. 



The limestone is considerably affected by the pyrites, 

 and being in some places, as we were informed, magnesian, 

 it gives rise to sulphate of magnesia, which might also 

 probably be worked to advantage. The pyritous beds of 

 limestone are only such as come into contact with the coal, 

 the superior strata are said to be quite free from it. 



The only circumstance worth mentioning concerning 

 the coal mines is, that they have frequently been on fire, 

 and that there are many indications of conflagrations at a 

 more remote period, probably caused by the spreading of 

 the fires lighted at the surface by the Indians to facilitate 

 their hunting. From these conflagrations the slate is in 

 many places observed to be quite altered in its appearance, 

 so as to resemble porcelain jasper in its characters. 



No iron ore has been found in this neighbourhood, and 

 we looked in vain, for indications of the argillaceous car- 

 bonate of iron, so usually to be met with in coal fields. We 

 were informed that at some distance from the town, large 

 quantities of iron ore had been discovered, but which from 

 the characters ascribed to it we were induced to believe 

 were not the argillaceous carbonate, but the oxide and 

 hydrate of iron. 



Having thus presented in one connected view, the vari- 

 ous geological observations which were made on this 

 part of the route, we return to notice the other interesting 

 circumstances which attracted the attention of our party. 



The route which we travelled is far more interesting to 

 the general observer than that to Pittsburg, the country 

 along the Potomac offers many very fine views, among which 

 none is more remarkable than that from Sideling-hill. The 

 ranges of mountains as they then present themselves, strike 



