Z 
a 
S. W. Ford—Age of Slaty and Arenaceous Rocks. 397 
tum, and in the “black band” beneath it. As these pitch to 
the north at an angle of not more than 25° with the horizon, 
they pass away from the recent works, so that they were not 
proven by the sinking of shaft No. 3, or the levels connecting 
with it, These beds should carry copper in the vein as they 
descend northward toward the lake. 
held on its way to the lake along the course of the vein, and 
did not then turn to the left, as it does at present. Without 
doubt its bed continued straight along the face of the rock seen 
in the adit A, A, and 35 or 40 feet beneath it, and presented at 
feet, by the agencies that brought in the drift material. During 
the period next preceding the drift epoch, and while the stream 
of water ran along the back of the vein, it wore away the vein 
touth, 
Captain Paul represents the vein in the “sand galleries” 
(galleries excavated in drift material, instead of rock] along its 
Whole exposure of more than 400 feet, as well charged with 
“opper, and is confident that the same “ pitches” of rock carry 
Copperin masses. The floor of the ‘sand gallery” is about 175 
feet above the lake. The dip of the strata carries the copper- 
ring; beds to the north, as they descend, about two feet 
horizontally for one vertically, or « distance of 350 feet in the 
depth of 175, i. e., to the lake level. The true approach to 
these beds is therefore from the north and at the lowest practi- 
cable level. 
ce 
Art, LUI.—Note on the Age of the Slaty and Arenaceous rocks 
. the vicinity of Schenectady, Schenectady County, N. Y.; by 
. D. 
Tum slaty and interstratified arenaceous rocks in the neighbor- 
hood of Schenectady, N. Y., have usually been referred to the 
“poch of the Lorraine Shales. They were considered to be of 
that age by Mather, who gives several sections of them, in their 
More eastward extension along the valley’of the Mohawk, on 
Am. Jour. Sc1.—Turep Serres, Vou. XXIX. No. 173.—Mar, 1885. 
27 
