4^ Editorial Comment. 
not far from the Calumet and Hecla mines. Here the horizon- 
tal eastern sandstones are represented as turned curvingly up- 
ward, and on their approach to the rocks of the Keweenaw 
series, to assume verticality, and in that position to be luiconform- 
ably overlain by porphyry conglomerate and diabase belonging 
to the Kewcenawan rocks, the latter dipping northwestwardly 
at an angle of about 42 °. They are separated by a mass of 
breccia and decayed rock, which has a thickness of about twelve 
feet. 
About a mile south from the Wall ravine is the St. Louis 
ravine. The same structural features are here repeated. The 
dip of the Keweenawan rocks, consisting of felsitic conglomer- 
ate, amygdaloid and diabase, is 47 ^ toward the northwest. 
** The sandstone at the junction, and its included bed of con- 
glomerate, dip toward, or beneath, the Keweenawan I'ocks, at 
an angle of about 70 ° , striking with the face of the hill, or 
N. 40 ° to 42 ^ E. These measurements w ere made on the 
junction between the sandstone and an included conglomerate 
layer, so that no room is made for doubt as to their correctness.'* 
(p. 28.) This plunging of the sandstones beneath the trap 
rocks, is said by the authors to be due, however, to an overturn 
dip in the sandstones, by which they conceive them to turn back 
beneath the surface at a great depth, passing through verticality 
to a high dip in the opposite direction, then to a low dip, and 
then to near horizontality. This rather remarkable interpreta- 
tion is said to be substantiated by exposures of vertical beds of 
sandrock in the bluffs of the ravine at several points below the 
place of contact. 
Again in the Douglass Houghton ravine the same combin- 
ation of stratigraphic phenomena appears. This ravine has 
been examined by J. W. Foster at different times. He regarded 
the eastern sandstone as more recent than the diabase and amyg- 
daloid and conformable upon them, upheaved by the igneous 
force that produced the outflow of eruptive rock. Mr. Alex- 
ander Agassiz in 1867 discredited the view of Foster and Whit- 
ney and showed that the eastern sandstone is unconformable up- 
on the trap rock of the Keweenaw range. Prof R. Pumpelly 
in 1870-72 adopts the view of Prof Agassiz, but rejects especial- 
ly the idea of a fault or dislocation which some earlier geologists 
