GEOGNOSY OF THE APPALACHIANS. 471 
ascending order are not less than 2000 feet of limestones with 
Trenton fossils (embracing probably the Chazy division), while to 
the east of this the Levis again appears, including the white Stock- 
bridge limestones.* We have here an evidence that the augmen- 
tation in volume observed in the lower members of the Champlain 
division in the Appalachian region extends to the Trenton, which 
to the west of Lake Champlain is represented, the Chazy included, 
by not more than 500 feet of limestone. The Potsdam, in the latter 
region, consists of from 500 to 700 feet of sandstone holding Cono- 
cephalites and Lingulella, and overlaid by 300 feet of magnesian 
limestone, the so-called Calciferous sandrock. In the valley of the 
Mississippi these two formations in Iowa, Missouri, and Texas, 
are represented by from 800 to 1300 feet of sandstones and mag- 
nesian limestones, while in the Black Hills of Nebraska, according 
to Hayden, the only representative of these lower formations is 
about one hundred feet of sandstone holding Potsdam fossils. 
striking contrast to this it has been shown that along the 
Appalachian range from Newfoundland to Tennessee these lower 
formations are represented by from 8000 to 15000 feet of fossil- 
iferous sediments. It has been suggested by Logan that these 
widely differing conditions represent deep-sea accumulations on 
the one hand, and the deposits from a shallow sea which covered a 
submerged continental plateau, on the other ; the sediments in the 
two areas being characterized by a similar fauna, though differing 
greatly in lithological characters and in thickness. To this we may 
add that the continental area, being, probably submerged and el- 
evated at intervals, became overlaid with beds which represent 
only in a partial and imperfect manner the great succession of 
strata which were being accumulated in the adjacent ocean. ł 
In a paper which I hope to present to the geological section 
during the present meeting of the Association it will be shown 
from a study of the rocks of the Ottawa basin that the typical 
Champlain division not only presents important paleontological 
breaks, but evidences of statigraphical discordance at more than 
one horizon over the continental area, which, as the result of 
widely spread movements, might be supposed to be represented in 
the Appalachian region. In the latter Logan has already observed 
* Amer. Jour. Sci., 227. 
Ibid., I, xxv, 439, xxxi, 234. 
t Ibid., II, xlvi, 225. 
