332 Association of American Greologists and Naturalists. 
Dr. Houghton said he could not speak definitely as to the 
contemporaneousness of the two formations, but he was sure of 
the similarity of their structure. ‘The copper in Michigan was 
frequently accompanied by zeolites and prehnite. 
B. Silliman, Jr. reminded Dr. H. of the discussion on this 
subject, at the meeting in Philadelphia in 1841, and stated his 
analysis of the Lake Superior copper in reference to its being an 
alloy of silver and copper, and also the silver on the copper to as- 
certain if it were an alloy of copper and silver; but he had found 
both the metals distinct and quite pure, although fused into per- 
fect union at their two surfaces. He would enquire of Dr. H. 
whether he had found silver under similar circumstances, and 
whether the silver was not segregated by the action of the dyke, 
and found in separate masses, and if it promised to be of any 
economical value. 
Dr. Houghton said the great mass in Yale College cabinet, 
referred to by Mr. S., was the only loose mass, where he had seen 
the silver and copper united ; he had been at the same vein that 
afforded this specimen, and had found silver distinct in branch- 
ing masses, but in very small quantity, and he had in one case 
found antimonial sulphuret of silver; the silver and copper were 
both very nearly pure. 
Dr. Beck said the facts in N. Jersey were of a similar character. 
On motion of the Chair, Dr. L. C. Beck, B. Silliman, Jr., and 
Dr. D. Houghton, were appointed a committee to draw up a re- 
port for the next annual meeting, embracing all the known facts, 
bearing on the occurrence of native copper, in the trappean re- 
gions of the United States. 
_ Mr. James Hall showed a specimen of the cherty limestone 
from near Niagara, as proving in a very conclusive way, the di- 
rection of the diluvial agency by which the surface of the rocks 
in situ had been ground down; in this specimen the nodules of 
chert had resisted the diluvial action and stood out in relievo above 
the surface of the stone, having before them a ridge of limestone 
which had been protected by the chert nodule. 
The Chair said he adverted to this fact last year, and consid- 
ered it as conelusive evidence against the hypothesis of simple 
aqueo-glacial action, as the cause of the smoothed and polished 
rocks; he considered that such an effect could result only from 
the sweeping over the rocks of a vast accumulation of angular 
