14 Messrs. Foster and Whitney on the 
The following is the synonymy of the groups of the systems 
developed in this region, according to the nomenclatures adopted 
in the reports of the different surveys. 
New York and Lake Superior. | Pennsylvania and Virginia. | Ohio, Iowa and Wisconsin. 
AZOIC SYSTEM. 
AZOIC SYSTEM. AZOIC SCHISTOSE SERIES. METAMORPHIC ROCKS, 
(Not classified in New York.) ‘(Wanting in Ohio and Iowa.) 
SILURIAN SYSTEM. 
rimeval st or ( Lower Sandstone, or For- 
Potsdam Sandstone. if ee Tes mation 1, wanting in Ohio 
wer Magnesia Linke 
Calciferous Sandstone. Lawes ‘part of tie Mateial sto ne oe e cigte n 2, want- 
Series, or part of No, IL. 
Trenton Group ees Poi Limestone, 
Chazy, osc and Black- Miridle. part aft Metre Blue Limestone 
river Limest oe ee - and Marls Ms “the West. 
ded as 
Galena Limestone (not re- be recognized in Penn- J the ais es “of Pike Cliff 
cognized in New York.) sylvania and Virginia. or — Magnesian lime- 
Hudson-river Group. Matinal Shales, or No. TIL ine “Bie "Limestone and 
end Sandstone and Clin- \e Part vs ey Piel a Series, Not round at the 
ton Group. r par 
Niagara Group. { Part os the Le tie Series, 
or part o Cliff ean of Ohio “ia 
per Magne- 
Onondaga Salt Group. Summit of the Levant Series, | sian te 
! 
ee 
[fs 
(i 
== 
DEVONIAN SYSTEM. f 
Upper Helderberg Lime- '  § Upper portion of the Cliff 
stone. Limestone. 
* * * * 
Azoic Series on the Northern Shore.—The rocks of which it is 
composed are developed on an extensive scale, both on the north- 
ern and southern margin of Lake Superior basin. Commencing 
on the northern shore of the lake, we find a series of taleose and 
chlorite slates with occasional beds of coarser grits, in immediate 
contact with the granite and gneiss. They have been divided by 
Mr. Logan, the distinguished Provincial Geologist of Canada, into 
two groups—a division which we have failed to recognize on the 
southern shore—the lowest of which consists of slates partially 
chloritic and talcose, and occasionally holding a sufficient number 
of pebbles derived from the hypogene rocks to constitute con- 
glomerates. “These slates,” he remarks, “are of a dark-green 
color, often dark-grey in fr esh fractures, which at the base, appear 
to be occasionally interstratified with beds of a feldspathic quali NYS 
of the reddish color belonging to the subjacent granite and gneiss 
sometimes they are a combination of feldspar and quartz, occasion 
Salancieieiennecniientcinadiitadineiceme acs a. 
emer 
= e 
