ROCK FORMATIONS OF THE WESTERN STATES. 
501 
toward the perfection of this nomenclature, the place of greatest development in the district 
under consideration should give the name. 
This examination westward also afforded a good opportunity of testing the value of fossil 
characters, when applied to the same strata extending over wide tracts of country; and the 
results will be seen, as we proceed, to have been mostly satisfactory. The value of litholo¬ 
gical characters at the same time was found to fail in a great degree, and though in some 
cases persistent, yet alone they would be found insufficient, and often lead to erroneous con¬ 
clusions. From the investigations made in New-York, we had learned that groups, which 
at one extremity of the State are of great importance and well characterized by fossils, cannot 
be identified at the other extremity; and the same is more emphatically true of single rocks. 
The Niagara group, so well defined by the topographical features of the country, as well 
as by both its fossils and lithological characters, no one has yet attempted to identify to the 
east of Little-Falls. Almost the same may be said of the Onondaga salt group and the Me¬ 
dina sandstone; while on going in the opposite direction, we find several important members 
of the Helderberg series entirely wanting west of Cayuga lake, and the Oriskany sandstone 
existing only in patches here and there. 
The undisturbed range of these deposits, with the great extent of unbroken outcrop bor¬ 
dering the Ontario valley and its continuation along the Mohawk, has enabled us to acquire a 
very perfect knowledge of the changes in the character of strata in their east and west exten¬ 
sion. While such changes have taken place in important groups, others of less apparent 
importance and of much less thickness are found remarkably persistent. 
In making my examinations westward, the groups and individual rocks of New-York, as 
adopted in the annual reports, were made the basis of reference. 
The Lake Erie shore, from the New-York and Pennsylvania line (a point to which pre¬ 
vious investigations had extended) to Cleveland, presents nothing of peculiar interest, being 
occupied by the rocks of the Portage group, which for the most part are destitute of fossils, 
except the remains of marine vegetables and a few Goniatites. The accompanying section 
(Pl. XIII) extends from Cleveland to the Mississippi river, and no rock is represented which 
was not actually seen. Westward, from Leavenworth, Indiana, it passes a little north of 
the line examined, in order to present the great limestone formation on the Mississippi, as a 
more prominent feature than further south, it being low and obscure near the mouth of the 
Ohio. 
The rocks seen near Cleveland, Ohio, are perfectly identical with those of the middle por¬ 
tion of the Portage group, or Gardeau flagstones, being a continuation of the same as traced 
from New-York along the lake shore. In following the road to Cuyahoga falls, the Portage 
sandstone, or upper part of the group, is seen at Newburgh, and is there underlaid by green 
shale. These are equivalent to the Waverly sandstone of the Ohio Reports, as was after¬ 
wards ascertained by visiting the quarries at Waverly. From Newburgh we pass over the 
shales and sandstones of the Chemung group, till we arrive upon the conglomerate which is 
well developed at Stow and Cuyahoga falls. 
