Geology and Natural History. 397 
stone beds in the lower part of the limestone formation. The 
position is said to differ from that of the beds in the Lehigh 
ion and i 
tween the limestone and the overlying Hudson River shales— 
which shales are yrange schists (hydromica schists) in south- 
lva 
Professor LestEy, who bins s long studied the ore beds, speaks of 
“shafts passing through soft beds of ore and hard ribs of lime- 
stone;” of the ore eds in one place “ visibly interstratified with 
the soft clay and solid limestone layers, ee the strike and 
sg and with regard to a large and ical ri bed, the 
“* Pennsylvania Furnace ore-bank,” he pret that the various 
irregularities in the deposits are owing to chemical oe aa and 
consequent changes in bulk in the strata, during the process of 
oxidation and solution in progress, in which the looser ealciferous 
and ferriferous layers lost their lime constituent, packed their 
sand and clay, and oxidized and hydrated the iron, thereby 
excavating caverns, depositing the iron precipitates as ore, and 
without much disturbance of the general stratification. “ Only 
pina lime-iron deposits as were properly constituted 
in oe have been so completely dissolved as to sige the 
stone; t s most gnesian or tic below, but that 
dolomite and limestone succeed each other in many alternating 
layers. He concludes that the iron of th deriy 
from the limestone, in which it had existed as a ferrous carbon- 
ate; that part of the limestone affords on analysis one to two per 
cent of iron, and that this is s ee epaiemn for the production of. the 
largest ore beds; wer the s as come from arenaceous lime- 
stones, or caleareous sand-ro mee rather than from sandstone,.and 
the clay from argillaceous limestones and intercalated shale ; that 
the oxidation of the iron took place in situ; that some "sma 
