Copper and Silver of Kewenaw Point, Lake Superior. 85 
strata, after passing between them, just as they do at Nova Scotia, 
and on the Connecticut River, and at New Haven. 
Having given some account of the sandstone strata, I would 
observe that the conglomerate rocks belong to the same system, 
and are evidently formed from the coarser pebbles and gravel, de- 
rived from primary and intrusive porphyritic and trappean rocks. 
The pebbles are all rounded and smooth, indicating the long con- 
tinued action of water, and abrasion of the fragments of rock by 
attrition, in a manner similar to that we now observe on the sea 
coast, where the surges of the ocean are continually at work, 
grinding the loose stones against each other. 
_ No remains of animals or of plants, unless indeed some obscure 
traces of Fucoides, have yet been found in the Lake Superior 
sandstones or conglomerates, and I understand that Dr. Houghton 
thinks he has satisfactorily traced this deposit below the coal bear- 
ing strata. If this should be fully established, the formation 
would be ranked as belonging to the old red sandstone series, al- 
though it so strongly resembles the sandstones of Nova Scotia and 
of the Connecticut River, that I have been disposed to regard it as 
higher in the series, and suspect it to belong either to the Permian 
or new red sandstone series; perhaps we have not yet sufficient 
data to fix the relative ages of any of our sandstone rocks, and it 
might be a useful work for some geologist to devote some years 
to their special study. 'The absence of characteristic fossils, pre- 
vents the ready determination of their age, and it will be re- 
quired to trace the strata continuously until their relation to other 
rocks is known. 
The conglomerate on Kewenaw Point is composed, as before 
observed, of pebbles of the older rocks cemented together by the 
more finely comminuted materials or clays, originating from their 
decomposition and disintegration. That the rock since its depo- 
sition has been acted upon by heat, is evident, not only from the 
induration of the cement and adherence of the pebbles, but also 
from the latter being cracked through the midst and separated 
from each other. Deep chasms are thus not unfrequently pro- 
duced by the contraction of the sundered rock, and veins of cal- 
careous spar often occupy the spaces. The calc spar often con- 
tains filaments of native copper, with a little of the carbonate, 
the latter being produced only when the vein is exposed to the 
atmosphere. When these veins occur near the trap dykes, anal- 
