894 B.D. Irving—Huronian Series of Northern Wisconsin. 
I have myself recently completed a study of my field results 
over the Huronian belt of this part of Wisconsin, as also 
of over one hundred thin sections of the rock specimens gath- 
ered, and have made a section which I think may be regarded 
as final. A synopsis of this is given ieee as it will appear in 
vol. iv of the Wisconsin reports. I s say here that in 
selected specimens furnished by Mr. ulien. In the 
year that has elapsed since then I have , familiarized myself 
with this (to me) new, and all-important method of investiga- 
tion, and have examined sections from nearly every ledge o 
importance within the Huronian area. 
Synopsis of the ey of the a of the Penokee 
fiegio 
, Wiscon 
AURENTIAN. 
Chloritic hornblende-gneiss and pink quartzose granite. 
HURONIAN. 
(Non-conformable with the Laurentian.) 
Formati Average thickness. 
I. ‘Tremolitic (Julien) crystalline dimestone exiacns Go Me 
Il. (A) Arenaceous white quartzite, often ‘uesttinced 35 ft. 
Magnetitic quartz-schi eee <ause oe AO ft. 
ch 
or aa aon ever epadbetie any bctphied material 410 ft. 
ti 
Saba like (c) but ee charged with mien or 
uart: 
Kinds (a) to (d) all carry much pyrolusite, or other 
manganese oxide. These varieties have e no pean 
stratigraphical arrangement, and are nam 
order of relative eine. Total thickness bas 780 ft. 
