IRON ORES OF THE AZOIC BELT IN PENNSYLVANIA.
The Primal and gneissic rocks are less elevated in Eastern Virginia, Maryland, and Pennsylvania than in North Carolina and Tennessee to the south, or in the States lying to the north. They seldom form mountain-ranges in these Middle States, as they do in the Southern and more Northern States. Trappean dikes and the evidences of volcanic outbursts or vents are numerous, and trap rocks of all remote periods are scattered over the greatest part of the gneissic area; but we rarely find beds of magnetic ores to compare with those of the former States. The beds which are developed are in a line of strike coincident with the magnetic ores of New Jersey, and in the lithological strata containing them in North Carolina.
The Warwick mine occupies a position between the lower Palmozoic and the azoic, and the ores are only partially magnetic, changing to brown hematites in their upper strata. This is, however, a true bed, and has been for a long period productive.
Starting from a point near the New Jersey line, northeast of Easton, we find a con tinuation of the New Jersey magnetic ores developed in Lehigh Hill, though in limited quantities; again in the Durham mines, south of the former locality. Here the ore is good, and the bed from 2 to 14 feet thick. Still further south we find the Mount Pleasant mines, and near Reading the Penn's Mount mines. Following this general strike, the magnetic ores are found in limited quantities into Maryland; but they depre ciate in quantity and quality from the Lehigh south, and but little productive magnetic exists between that point and the mountains of North Carolina, when compared with the immense masses developed in New Jersey, New York, and the Azoic range to the north.