T. B. Brooks—Rocks observed in the Huronian Series. 195 
sian, argillaceous, and micaceous rocks. An effort has been 
made to reconcile these different views through the results of 
the microscopic investigations of the gentlemen above named, 
as well as by observations in the field, where a fine-grained or 
altered rock can often be traced through its various transitions 
to a coarser and typical variety. : 
The age and distribution of the different members of the 
Huronian series given in the annexed table are chiefly based 
on my own observations; use, however, has been made of the 
notes of Prof. Pumpelly and Mr. Wright, and the publications 
of Dr. Credner, whose descriptions of the transitions of the 
various rocks are excellent. The hypothetical scheme of 
equivalency presented in the table is my own.* That subject 
was also discussed in a paper entitled, ‘On the youngest 
- Huronian Rocks south of Lake Superior, and the age of the 
pps ere Series.”+ 
ones he examined) in the Menominee Region. In one instance, 
however, owing to his having mistaken cleavage for bedding 
planes (bed IX), he overlooked at least one synclinal and one 
anticlinal fold, thus counting the same bed at least three times. 
uronian of Canad 
i siete es my oldest fourteen beds of the Marquette series the 
deutschen bed I the Menominee series. See Zeitschrift der 
ognize geologischen Gesellschaft, xxi Band, 1869. His having failed to rec- 
eenize the upper Huronian, detracts considerably from the weight of this hypoth- 
Published in the jae 
~ proceding volume of this Journal, page 
feo enn, the proce in the above note. 
