12 N. H. Winchell on the "Original H^ironian.'" 
himself, so far as I have been able to learn; while Mr. Logan, 
who studied it later on the shores of lake vSuperior where the 
rocks that Mr. Murray described on the north shore of lake 
Huron appear on the lake Superior shore, amplified the forma- 
tion by adding some strata, or some phases of the strata, that are 
not mentioned by Mr. Murray. Later still, following the defini- 
tion of the horizon which it was supposed the Huronian occupies, 
Mr. Bell and Mr. Dawson, as well as nearly all American geol- 
ogists, have swept under the same designation several lower, 
and quite distinct, stratigraphic terranes. This confusion was 
intensified bv the application of another name to a group of rocks 
in northern Minnesota and the adjacent parts of Canada, by Dr. 
Hunt, which it is the object of this paper to show is the same as 
the principal member of the Huronian in the original area of 
Murrav, on the north shore of lake Huron. This new name, the 
"Animike slates and quartzytes," was thought by Dr. Hunt, to 
cover a series of strata much later than the Huronian; and even 
later than the copper-bearing rocks of lake Superior. They 
have been found, how^ever, to run below the copper-bearing 
rocks, and to constitute a great formation whose extent in 
Minnesota has been found to be at least a hundred and twenty- 
five miles, and whose equivalents in Michigan and Wisconsin 
are gradually being identified. 
Mr. Irving, who has examined the area of the original Huron- 
ian within the last two 3^ears, has called attention to the nature 
of the strata of which it is composed. His general description 
is the same that I should give, with the exception that I should 
not apply the term gray-ivacke., to any of the rocks there found. 
The gravwackes, so far as I am acquainted with them, appear 
in the Marquette and \"ermilion iron regions, and probably in a 
lower formation; the strata to which Mr. Irving seems to have 
applied this term are quite different from the gravwackes seen 
in the iron-bearing rocks at ^'eru^ilion. Instead of being 
coarsely granular, largely made up of feldspathic material and 
of a gray color, the beds of the Huronian are mainlv siliceous, 
fine-grained and of a rather firm texture. They are inter- 
bedded with, and pass into, fine-grained carbonaceous slates. 
They are better described taken altogether, as black slates and 
q7iartzytes. 
