J. D. Dana on American Geological History. 318 
This key soon opened to us a knowledge of New En land 
geology, mainly through the labors of Prof. Hall, and also o 
essor H. D. Rogers, following up the survey of President Hiteh- 
eek and now the so-called a imary r sone anite, gneiss 
Let us now briefly review sis succession ine epochs in American 
geological histor 
= The Azoic Age ended, as was observed, in a period of exten- 
__ Sive metamorphic action and disturbance,—in other words, in a 
vast revolution. At its close, some parts of the continent were 
deft as dry land, which appear to have remained so, as a general 
x thing, i In after times ; for no subsequent strata cover them. Such 
es ao ee 
= -~ yap G. Troost — args J. — ee of Sig ennai J. GREENE, te Locks, 
HITTLESEY, [. A. L G. C. Swattow, J. G. Norwoon, B, F. Suuarp, be- 
ss = he invetigatrs in i Cade. Sir W. E. Logan, J. Meslay J. W.. Dawson, 
UNT an 
ers, 
othe Carboniferou oe was early studied in many of its details by Dr. 
Hucprern. But successive strata of the whole formation from the Devoeinn 
through ¢ the Stbearboniforoue and Coal Measures, were first systematized by the 
Professors Rogers, th ough without yet marking out in any of their publications the 
isi 1 measur mselves an char: 0 
____ ¥esearches on the coal beds have been ie by R. C. Tartor J. P. Ls 
Pennsylvania, J. Hatt, D. D. Owen, and others in the states of the Miispp val valley, 
: J.8. Newzerry on the fossil plants and fishes of the Ohio coal measures 
and C. T. Jacksoy on the coal beds of Rhode Island; Dawson, Lyrtt, Jackson, pat ; 
on the New Brunswick Scotia beds ; a Wraan, Lavy, Lye, an 
ro 
bier i and continues still his bavedtieti The examinations of Dz 
yan besitos defining the limits of our De rennin also contributed much on 
, la red ‘sandstone and tra regions of the Triassic or Jurassic period, w 
in the Connecticut valley aul in pr? Beng oh parallel with the Atlantic ber 
der to the south, and also to the north be Scotia, have been specially 
investi by D. Otmsrep, E. Hrroncocr, J. G. Perctvat, Professors Rocrrs, E. Ex- 
ACKS 
Q 
i 
zt 
: 
my 
é 
% 
I 
BS 
? 
-Deanz, W. C. 
Lza, and Prof, Owen of London; i th the hails by the Profimects Rocers, 
» Siarn€ CHCOOEK, JF. 
_ * The labors of Sir W. E. Locan have thrown great reat Pe Sia New England 
and ar iving | —— ad our i dge hitherto unattained. He 
esa 
Fe 
a3 
" 
wait 
peu 
a 4 
BB 
EF 
a 
8 
z 
d 
¥ crystallin ng, a in 4 
are there uncr a a and fostieoa and thus is putting the question o 
rkshire li has thus 
me erent as at as in New Sis: : the pet Pa mica slate o agate Ver- 
% o be Upper Silurian in ae it being uncrystalline lim —— . 
panes aly etamorphic and still containing distinct traces of 
abe i ns oa and Lake Memphremagog, and farther south 
= ~e more crystalline as Il as calcareous | and losing all indications of fossils. 
S. Hunt of + other facts to bear on this subject. 
 eleomp SERIES, VOL. XXII, NO. im OV 1896. 
40 
