188 AGE OF THE RED SANDSTONES 
If, in the absence of conclusive palzeontological evidence, the test of lithological 
character alone be applied, it must be admitted to favour the view, that they are of 
the same age as the red sandstones of Virginia, Maryland, New Jersey, Connecticut, 
and Nova Scotia. Specimens of the red sandstones of the south shore of Lake 
Superior (in Wisconsin), including the buff beds associated with them, cannot be 
distinguished from specimens in my collection, procured from the quarries of Seneca 
Creek, in Maryland, of Acquia Creek, in Virginia, and of Little Falls, in New 
Jersey; all of which are generally admitted to be of cotemporaneous origin.* 
Some of the results from chemical analysis seem also to favour the same hypo- 
thesis. Taken as a whole (though with exceptionst), the sandstones of Lake Supe- 
rior contain a considerable percentage of alumina, ranging, sometimes, as high as 
twenty per cent.; while of silica there is often less than fifty per cent. Their 
peculiar red colour is due to the presence of a large proportion of peroxide of iron, 
this latter opinion. In the report of the proceedings of the Association of American Geologists for that 
year, we find the following : 
“Dr. Houghton said, that the sandstone of Lake Superior, lying east from Keweenaw Bay, dips, at a 
moderate angle, to the south, or a little east of south, and passes under a lime-rock, which he considers 
to be the equivalent of the Trenton lime-rock of New York; while those conglomerates and sand-rocks 
lying westerly from Keweenaw Point, and flanking the trap on the north, dip to the north, mostly at a 
high angle. These last-mentioned rocks are probably cotemporaneous with the New Red, and were doubt- 
less deposits during the long interval that marked the upheaval of the trap,” &c. 
I have sought for, but not met with, any subsequent statement of Dr. Houghton, reversing this opinion. 
My own first impressions, during the explorations of 1847, favoured the same view of the case. In my 
provisional Report, of 1848, while asserting that ‘‘it is impossible, at present, to decide between these 
conflicting opinions,” I added: “ Judging from lithological and mineralogical character, sy certainly 
is strong presumptive evidence, that they were deposited subsequent to the carboniferous era 
It is only after a careful review of all the facts bearing on this question, collected by myaelf and other 
members of the corps, that I have finally reached the conclusions given in this chapter. I doubt not, 
that, had Dr. Houghton’s valuable life been prolonged, he also, after examining the problem in all its 
bearings, would have seen cause to give the weight of his authority to the opinion, that the red sandstones 
in question are of Lower Silurian date. 
* It was formerly the admitted doctrine, that these sandstones are of New Red date, the equivalent of 
the Gres de Vosges of Alsace, the Bunter Sandstein of Germany, and the Triasic System of recent writers. 
However, the opinion has been advanced by some, that the lower beds of red sandstone running through 
the older States, are of a date anterior to the coal; perhaps, Upper Silurian ; perhaps, like the sandstone 
of Lake Superior, which, in aspect and composition they so much resemble, Lower Silurian. With so 
much uncertainty still hanging over the date of a formation so long submitted to the oldest and most 
experienced geologists of the Union, it is little surprising that a series of rocks in the remote West, similar 
to the others, alike in their appearance, and in the absence of acknowledged characteristics, should have 
caused doubt and variance of opinion, before, at last, after thorough and minute exploration, their true 
age was satisfactorily explained. 
_  } As shown, for example, in the following analysis of red sandstone from Madeline Island, one of the 
Apostle Group, off the south shore of Lake Superior : 
Insoluble silicates, : ; oF . : ; 93°5 
Tron and alumina, : ; : : ; ; ' 3-9 
Carbonate of lime, 3 ae : ; ; : 1-0 
Carbonate of magnesia, : ; , : . a trace. 
Loss, . . - 6 
