22 T. B. Brooks—Lower Silurian rocks 
Haines of New Jersey. The cabinet of Mr. Haines contains 
many hundred specimens, and I am greatly indebted to his 
gpeton for the privilege of examining them at my Acct To 
eymour and Professor Brush I would also express my 
gratefal acknowledgments. The complex form represented in 
figure 8 is from a crystal in the cabinet of Mr. Seymour. 
New Haven, Ct., May, 1872. 
Art. V.—On certain Lower Silurian rocks in St. Lawrence county, 
N. Y., which ue e grobaky older than the Potsdam Sandstone ; 
by T. ’B. BRoo 
A survey of the Caledonia and Keene iron mines at Keene 
Station, St. Lawrence county, New York, made by me in the 
spring of 1870, developed the following series of sedimentary 
conformable rocks, some of which are apparently older than the 
Potsdam 
In descending order the series is as follows:—Ist, A fine 
grained, somewhat friable light Bray, sometimes reddish, ait 
stone, which toward the bottom of the bed is often a quartz 
conglomerate. It is lighter colored and less firm, but otherwise 
resembles the sandstone quarried at Potsdam. The maxi- 
mum thickness observed was, say 40 feet, but the line separat- 
ing this rock from No. 2 was not always well-defined, and the 
surface was lowered from erosion. 
This rock is named by Dr. Emmons Potsdam sandstone 
page 93, Part rv, Geology of N. Y., where the Caledonia Mine 
is described under the name of the “ Parish ore bed.” 
2nd, Next below this sandstone is the iron ore formation ; 
made up of red hematites, both specular and earthy, together 
with irregular lenticular masses of a brownish and very 
compact sandstone or quartzite, and a magnesian rock resem- 
bling No. 3 of this series. Associated with the ore are the car- 
nates of lime and iron and other minerals: carbonaceous mat- 
ter is shown by the analyses. This formation varied greatly in 
thickness in different localities, from a few feet to at least 40. 
The mines which are now extensively worked are in this 
formation. 
8rd, Under the ore, and forming the foot wall of the mines, is 
a soft rock, generally schistoze or slaty, but sometimes massive 
in structure, of a green to grayish-green color, a lead 
te and rere porous where exposed in outcrops. It is ap- 
eyK wes oe rock, containing considerable graphite and 
iron regis ne esignated by Dr. Emmons as serpentine, and 
: 
a 
5 
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