White Limestones of Sussex County, N". J. — Nason. 163 
There are many other localities which could be mentioned, 
but instances would only be multiplied. 
Southward from Mine hill the writer has found nothing 
which could be called transition zones, nor have samples been 
collected for anatysis. Frequent tests were made with acid, 
and both the limestones were found under the same conditions. 
In the "Geology of New Jersey," 1868, pp. 401 and 402. Dr. 
Geo. H. Cook has given several analyses of the extension of 
this same formation to Sparta, six miles south of Franklin 
Furnace. 
a. b. c. 
Lime 51.07 28.31 29.68 
Magnesia 3.02 18.01 20.07 
Carbonic acid 47.47 42.08 45.51 
As only the relative proportions of lime and magnesia are essential 
the analyses are not quoted in full. 
a, crystalline white limestone, Sussex lead mine. 
b, " " " Sparta. 
c, " " " Ogdensburgh. 
The exact localities of the first two are unknown. No. c is, 
however, known exactly. At the Stirling hill mines a tunnel 
has been driven into the hill to intersect the zinc bed. This 
specimen is taken from this tunnel. It is highly interesting. 
since it shows that the zinc deposit at Stirling hill has a dolo- 
mitic limestone for its country rock, in part at least, as well 
as a nearly similar deposit at Mine hill. 
Though there are analyses which show, according to Dr. 
Cook, still smaller percentages of magnesia, it seems as if the 
point is-well established that the white limestones are gener- 
ally dolomitic, and are, excepting under peculiar circn in- 
stances, but slightly niagnesian, and that, whatever argument 
may be brought up in £he future against the writer's views of 
a contemporaneous origin, this point cannot he urged against 
them. 
It is but simple justice both to Dr. ( look and to Prof. Nmoek, 
so long a time his assistant, to sa} r that they were well aware 
of the problems connected with the white limestones of Sussex 
county. In a recent conversation with Prof. Smock, lie said 
that both he and Dr. Cook had visited man} r of the localities 
named by the writer, and on the ground had discussed the ques- 
tion of transition and chemical composition; and that at one 
