402 The American Geologist. December, 18% 
Cambrian, and not Potsdam sandstone, as it has liitliorto been 
called), and modern placers along present stream beds, result- 
ing in part from the disintegration of the older placers. The 
so-called siliceous gold ores occur in the remnants of Cambri- 
an beds and included porphyry bodies in the elevated region 
around Grey's peak and Bald mountain, to the west of the 
Homestake belt. The ore bodies are siliceous replacements of 
certain beds in the upper and lower parts of the formation 
near eruptive sheets or dikes, which have been mineralized 
from certain north and south cracks or fissures — locally called 
"verticals" — which traverse both sedimentary beds and erup- 
tive sheets. The ores are finely disseminated pyrite, generally 
oxidized with gold, either free or combined with tellurium.. 
The ore bodies are of great longitudinal extent, having been 
traced continuously in the Golden Reward main for many 
thousand feet; in some cases they are twelve feet thick and 
more than'a hundred feet wide. They give promise of im- 
portant future developments. 
New York Academy of Sciences; Section of Geology and 
mineuaeogy, october 19, 1896. 
The first paper of the evening was by Arthur Hallick, enti- 
tled Geohxiiral Notes; Long Island and Block Island. Pre- 
vious investigations on Staten island. Long island, Martha's 
Vineyard and Nantucket have proved a unity of geologic 
conditions throughout, and it was confidently expected that 
a careful examination of Block island would show this also 
to be part of the same general series. 
During the past summer the island was visited and proofs 
were obtained of drift phenomena identical with those of the 
other localities. A collection of fossils was made which dem- 
onstrated the former existence of Cretaceous strata on the 
island. The material collected consisted of plant remains, 
imperfectly preserved, and of mollusks in a good state of 
preservation. These latter were identified by Prof, R. P. 
Whitfield, and the list numbers ten species, in addition to 
fragmentary remains of perhaps half a dozen more. They are 
typical of the lower green-sand marl and were found as drift 
material in the moraine, under the same conditions in which 
similar fossils have been found in the other localities men- 
tioned. It was also thought advisable to again visit the east- 
ern end of Long island in order to ascertain whether more 
definite fossil remains could be found on Montauk point, 
where imperfectly preserved fossils had been discovered on a 
jorevious occasion. Here also well-preserved mollusks were 
found, likewise identified by Prof. Whitfield, who has furnished 
a list of five species and two genera, in addition to which a 
number of imperfect specimens, representing about five addi- 
tional species. The discoveries were highly satisfactory, and 
