— 137 
is any reason for blame, with his familiarity with the Triassic and Oolitic 
rocks of Europe, in his Pua out the lithological resemblance there 
may be between them, any more than there is ground for bl: 
American geologists ae after identifying certain beds in New Jersey as 
Cretaceous, have also ene: to their mineralogical re cay angle with the 
Green Sand of Euro ; for this is, after all, a remarkable fact which runs 
over immense tracts of geological deposits belonging to ik same horizon, 
rag to Stic Agassiz on Marcou’s Geology of North America, by 
James D, D I regret in such a case as this to have to differ from 
Probeckor resale The amount of difference is however not as great as 
at the first reading may appear; for an important part of the positions in 
my paper are untouched, and an explicit dissent from some of the views 
of Mr. Marcou is expressed, 
The a. in Professor, Agassiz’s remarks to be especially noted 
are the follow 
1. 
5 
. 
209 
= & 
seen the at papers ae Mr. Marcou and examined his ‘saloon map. 
2. That while, as regards the geology of the East from lowa to the 
Atlantic coast, “to Mr, Hall is due unghie ane the eredit of having 
Settled by extensive comparisons and by personal examinations the true geo- 
re horizon of the vastest pron of our ; oAteenE not only by examina- 
n of the Superposition of the ocks, but also on the es minute and 
have done much to elucidate the ii pial geography, the orog aphs , and 
the order of Succession of the formations of Pennsylvania and Virginia, 
and have thrown much light upon the general geology of the eastern part 
of the Continent,”—west of the meridian of Iowa their observations aoe 
not eitien and Marcon has thence the advantage 0 of t them. < 
. That the maps of the region west of the papel by Rogers, 
Tall, and Marcou are mainly sin ine — p ults of various 
'on over the 500 000 square miles of “the Rocky’ mountains, and. ohag 
own also the Permian and Jurassic over the same region, wep bas 
culpable than Hall or Rogers in covering it with Cretaceous. | 
on Hl Paeoon i is mistaken in regarding the Lake Superior n 
iassi 
Py That it is hardly credible that Mr. Marcou should have bi : 
completely risen in his identification of Oolitic beds in the west; and. 
that the two's species ae b by Marcou from the beds are most allied, 
Professo 
£assiz’s opin ¢ species 
re Mareou pels ta neologen characters are’ of .no value 
a identifying geological horizons ; and that adding these characters to 
Bim general evidence for the’ Triassic and Oolitic rocks is not blameable.. 
< claims which Mr. Mareou has il forward in his work are: (1). 
the . 
t determination of the Red Sandstone of the Lake pet region ; , 
SCOND SERIgs, Vv, ox. XXViIl, No. 79, eo saa 
18 
7 
