56 E. B. Andrews—Parallelism of Coal-seams. 
The greater similarity of the Douglas County traps to 
leone of Isle halal than to those of Ashland County, goes to 
confirm m 
The dotted ee then, on the accompanying section give 
my explanation of the structure of this region, in accordance 
with the foregoing facts and views. 
It should be said that the trappean beds of Douglas County 
have been traced for some miles into the Bayfield peninsula, 
and can without doubt be traced still farther, ci that they can 
mous, 
int they must pass beneath the horizontal Re BEEN of the 
Apostle Islands, age of the coast of the peninsula. It should also 
b the area south of the Copper Range in 
Douglas County, aes the explored region and the line A 
B, which marks the supposed southerly edge of the partes 
side of the great synclinal, or else the line of the axis of t 
subordinate fold—which area I have supposed to be ‘ounods 
ately iaps ae by beds of the Copper-bearing Series—may be 
found to show horizontal sandstones, since there is no telling 
how ag these may have nee aes down on the upturned beds 
of the former mentione 
One more point suggests ‘iteelf as affording strong proof of the 
greater age of the Copper-bearing Series as compared with the 
orizontal sandstones. I refer to the ferruginous and aluminous 
character of the Lower Silurian sandstones of Lake Superior, as 
compared with the light-colored, quartzose sandstones of the 
Mississippi Valley, which are either approximately or identi- 
cally of the same age. If the Copper-bearing traps are older 
than the horizontal red sandstones, then the latter derived 
their material from the wear of these traps, which are remark- 
able for their low amount of silica, considerable percentage of 
alumina (feldspar) oe prevailing content of iron (as mag- 
netic iron). Man ese sandstones are almost a trap sand. 
The beds of the Missies pi Valley, however, derived their 
material from the wear of the Huronian quartzites, and Lauren- 
tian quartzose granites. 
University of Wisconsin, March 21st, 1874. 
Art. VITL—On the Parallelism of Coal-Seams ; by HE. B. 
ANDREWS, 
In the April number of this Journal, Dr. Newberry calls 
in question my views of the general arallelism of coal-seams, 
deriv: fe See ee our Ohio Gata censs nd thinks 
