.GEOLOGICAL SOCIETY OF PENNSYLVANIA. 191 



ded. The coal vein, so far as was penetrated, was irre- 

 gular as to thickness, ranging from five inches to as many 

 feet. 



Our notice of the Hopewell section, would be incom- 

 plete without adverting to its iron ores. 



Haematitic iron ore of great richness occurs in the 

 limestone valley on the east side of Tussey mountain. 



Hydmte of iron exists abundantly at the several points 

 indicated in the map and section, and has supplied the 

 neighbouring iron works for many years. It occurs 

 under a variety of circumstances and situations, lodged 

 on the summits of ridges or accumulated on their slopes, 

 at all elevations. For many years the supply of ore for 

 the Hopewell Iron Works was derived from the summit 

 of a ridge upwards of 600 feet high. The present sup- 

 ply for the same establishment is derived from the east 

 side the Ailegripus ridge, at a height of about 100 feet. 

 Like most of these ores, it is lodged in variegated clays, 

 in nests, in irregular seams, in dispersed angular frag- 

 ments, or in the form of ochreous incrustations and no- 

 dules. These clays are commonly covered to the depth 

 of ten or twenty feet with alluvium. Two other adjacent 

 deposits of this mineral also furnish ore to the same 

 furnace, and produce pig and bar iron of first rate 

 quality. These deposits are situated on the flank of a 

 thick series of red shale and red marly rocks, contain- 

 ing much oxide of iron. It is therefore probable that 

 these hydrates result from the decomposition of the fer- 

 ruginous strata.* 



It is a prevalent opinion, for which, from my own ob- 

 servation, there seems some foundation, that the richest 

 and most extensive depositions of this mineral occur on 

 the eastern sides of the ridges. 



* The yield of iron at the Hopewell Furnace is forty per cent on the raw 

 ore, and twenty-eight and a half per cent after torrefaction. 



