56 Editorial Connnent. 
recognized Keweenaw sandstones and conglomerates, so far as 
similaritv of composition constitutes a link of alliance between 
formations, and here it is a strong link, because it is as easy to 
explain the presence of those in the eastern sandstone, without 
invoking the presence of a sea-cliff, as it is those in the Kewee- 
naw sandstone itself. 
The concluding opinion of the authors, one which satisfies 
all the conditions of the case, of which they enumerate those of 
stratigraphic position and composition, and of general topo- 
eiaphic relations as brought forward by their discussion, is ex- 
pressed thus: "That the Keweenaw series is much older than 
the eastern (Potsdam) sandstone: that it was upturned, faulted 
along the escarpment, and much eroded before the deposition of 
the eastern sandstone; that the latter was laid down unconform- 
ably against and upon the former, and that subsequently minor 
faulting along the old line ensued, disturbing the contact edge 
of the sandstone." 
The document is undoubtedly one of the ablest discussions 
of stratigraphic problems that has ever been produced in America, 
and it will long remain a monument to the scientific skill and the 
genius of the authors, cere ferennius^ although it cannot be said 
to, close the discussion by that convincing array of evidence that 
the importance o\ the issue demands. 
One or two reflections, in conclusion, derived from the fore- 
going examination of the work, will be warranted at this place. 
1. It is a remarkable fact, admitted by the authors, and 
shown by <^heir diagrams, that the eastern sandstones pass be- 
neath the Keweenaw rocks at places along the south side of the 
range. Whatever be the true explanation of this fact, first in- 
sisted on with detailed description by Dr. M. E. Wadsworth, it 
brings ^^I'^oninently to mind another "view" to which the 
document makes no illusion, a iz. : that of Houghton, which main- 
tains that the trap- rocks of Keweenaw point, and of the copper- 
bearing scries in general, are not of paleozoic age, but mesozoic, 
being the equivalent probablv of the trap and brown sandstones 
of Connecticut. In consonance with this view are those facts 
appealed to by the authors that seem at variance with the 
Credner a lew, /. r., the contact of the two formations is not al- 
ways at the same stratigraphic horizon. There is an oblique over- 
