GEOGNOSY OF THE APPALACHIANS. 485 
the crystalline schists of the Green Mountains, he refers the 
gneisses and mica-schists of the White Mountains to the same 
system; while the broad area of similar rocks from their base to 
the sea at Portland, is regarded as Laurentian. This, on Credner’s 
map, is also made to include, with the exception of the White 
Mountains themselves, all the rocks of the third or White Moun- 
tain series which cover so large a part of New England. Those 
who have followed the historical sketch already given, can see how 
widely these notions of Credner differ from those of Emmons, and 
from all other American geologists, and how much they are at 
variance with the present state of our knowledge. It is much to 
be regretted that so good a geologist and lithologist should, from 
a too superficial study, have fallen into these errors, which can 
only retard the progress of comparative geognosy, for which he 
has done so much. In England, again, Credner confounds the 
Cambrian and Huronian, referring to the latter system the whole 
of the Longmynd rocks with their characteristic Cambrian fauna, 
a view which is supported only by the conjectured Cambrian age 
of the crystalline schists of Anglesea, which are probably pre- 
Cambrian and veritably Huronian, like the Urschiefer of Scan- 
dinavia ; which Credner correctly refers to the latter system, as 
Macfarlane and Bigsby had done before him. He, moreover, rec- 
ognizes in the similar crystalline schists of Scotland, the Urals, 
and various parts of Germany, including those of Bavaria and 
Bohemia, a newer system, overlying the primary or Laurentian 
gneiss, and corresponding to the Huronian or Green Mountain 
series of North America, while he suggests a correspondence with 
similar rocks in Japan, Bengal, and Brazil. In a collection of 
rocks brought from the latter country by Professor C. F. Hartt, I 
have found, as elsewhere stated,* what appear to be representa- 
tives of the three types of crystalline schists which have been 
distinguished in eastern North America. 
Ft will be noticed that I have not, in the preceding pages, 
referred to the Labradorian (Upper Laurentian) system, which is 
characterized by a great predominance of norites and hyperites 
Although occupying a considerable area in the Adirondack ragos 
it is not certainly known in the Appalachian range, and was, 
therefore, omitted in the discussion. In addition to the facts 
* The Nation, Dec. 1, 1870, and Hartt’s Geology of Brazil, p. 550. 
