L-sley.] J-W [Jan. -i and Feb. 6, 



Western Pennsylvania, in both contingencies an exploitation of ore must 

 be provided for, amounting annually to many hundred thousand tons 

 per annum. 



The largest mining operation in the Valley being that of the Pennsyl- 

 vania Furnace, Mr. Harden takes the account book of the works at that 

 point for a practical basis of calculation of the cost of exploitation. It 

 is evident that mining conditions through the Valley are very similar. 

 No system of between-rock mining will be required for many years. But 

 exploring drifts and shafts will be necessary, and vmder-cutting where the 

 clays are destitute of ore and too thick to remove. Most of the -work 

 however must be done in open cuts of great extent, with simple 

 machinery for obtaining water and washing the entire mass of ore- 

 ground to the very bottom, or to the deep rock-ores, which can be quarried 

 and used without washing. Ln many cases the rock-ore, and in some 

 cases the clay-ore, can be followed downward between solid masses of 

 limestone rock ; but this must be done in connection with the open-cuts. 



At the Pennington Banks there appear to be from 50 to 80 feet of 

 wash-oi-e and clays overlying from 8 to 16 feet of rock-ore. 



At the Dry Hollow Banks there is a stripping at the surface from 5 to 

 15 feet deep containing but little ore ; theu wash-ore with sands and 

 sandy clays to a depth of 20 or 30 feet before reaching I'ock-ore. 



At the Hostler Banks a top stripping of 5 feet or more, covers 50 to 

 60 feet of wash-ore in clay, under which lie the pipe-ores, which are re- 

 ported as having been in one place over 40 feet deep ; limestone layers 

 covering and dividing the mass. The miner who sunk the last shaft in- 

 formed Mr. Harden that it went down 60 feet through wash-ore, 5 feet 

 through solid limestone, and 7 feet in pipe-ore on one side of it, and 

 wash-ore on the other side ; water stopping further sinking. 



At the Pennsylvania Furnace Banks, the entire mass from the surface 

 to the floor of the quarry is wash-ore mixed with clay and sand. The 

 whole of this mass has been washed. "In one place a 13 feet face of 

 excavation gave 3 to 4 feet of surface soil and sienna-colored sandy-wash, 

 the remainder below it being a sandy, whitish ochre, and sienna colored 

 clay, streaked and marbled with red and brown, and some, not large 

 lumps of ore. Scattered through the whole, in considerable quantity 

 in some places, are small pieces of quartz which are picked out after the 

 ore has passed over the trays. In another part of the diggings this quartz, 

 from the size of shot to lumps 3 or 4 inches thick, is scattered through 

 the mass.* Some masses of this quartz, of one or two cubic feet in size, 

 lie about the quarry. 



"In a deeper part of the diggings where the face of ii-on and work 

 measures 45 or 50 feet, in two heights of 15 and 30 to 35 feet, now being 

 moved to the inclined plane for washing, the face is made up of sand and 

 various colored clays holding ore, all of which is washed. Limestone 

 appears at the bottom and pipe-ore has been found underneath it." 



* Mr. Harden gives an analysis of this quartz : Water, 0.50, Silica, 96.00, Iron and 

 alumina, 1.76, undetermined, 1 68. 



