EF. Prime, Jr.—TLimonite Deposits of the Great Valley. 487 
highly improbable that we shall find continuous deposits of the 
brown hematite ores when the slate or clay does not occur 
with them 
With respect to the quantity of ore, Professor Lesley, in his 
paper on the Cumberland Valley, says it will depend: ‘ First, 
on the original charge of iron in the strata; second, on the dip 
of these strata; and third, on the depth beneath water-level to 
which the mouldering decomposition of the strata and the per- 
oxidation and concentration of the iron has exten 
here is much difference of opinion as to how these deposits 
of brown hematite ores can have been forme r. Hunt, in a 
peas read before the National Academy of Sciences in Novem- 
1874, gives it as his opinion that they were sen beds of 
pyrites in Huronian schists, now decayed. I have shown in 
the commencement of this paper that they are ” Caleifero 
slates or he and were the ores formed b ee alteration 
beds in 1838 or 1839. urse, only the carbouslon of lime 
and magnesia would be dissolved; the clay, iron ase silica 
would remain behind. Were this, " however, the cas hould 
we find fresh, undecomposed damourite-slate os aie aa in ae 
tion with limestones above and below it, as can be seen at the 
Lehigh Iron Company’s limestone quarry ‘at Allentown, ar : 
From what I have seen in Lehigh, Northampton and Berk 
Counties, Penn., I have been led to the following conclusions 
which I advance with considerable reluctance, as I consider it 
extremely dangerous to argue from observations sere a lim- 
— area to general conclusions. 
Lesley, Report on the ematite deposits of the Nittany V: 
' Prof. C. U. Shepard, in his ble on the Geological Survey of Chavabtio 
published in 1837, says origin of limonite in these rocks [‘ 
slate, mi- 
gneiss or qu rock’] may be attributed to the decomposition of the 
sulphuret of iron and other fetta rruginous minerals with which they are known 
abound. It t is obvious also that, in a majority of instances, this change took place 
in the original repositories of these minerals; since no perceptible derangement 
Dana to accord fully with the various facts in the limonite region of 
Connecticut and Massachusetts. — 
