Geology and Mineralogy. 147 
Whitfield, illustrated by 27 lithographic plates; report on the 
ore deposits (lead, etc.) of southwestern Wisconsin, by Prof. 
Chamberlin ; on the crystalline rocks of the Wisconsin Valley, by 
R. D. Irving and C. R. Vanhise; and on other subjects. 
In the course of the part on General Geology, Prof. Chamberlin 
gives his views on the origin of the iron, copper and lead ores of 
the State. The great iron ore beds of the Huronian are regarded 
as originally deposits made in waters or marshes, approximately 
og ores are now made. The same view is held by Prof. Irving. 
The opportunities for observation which the Archean ore 8 
of the region afford give great. weight to the opinion of these 
geologists. 
The copper and silver of the Keweenaw formation are attributed 
to the same deep-seated source with the igneous rocks in and near 
which they occur, they having existed in some condition in tle 
eposits. 
rof. Chamberlin refers to the view (favored by the writer) 
determinable trom their outcrops, “ give no warrant for the sup- 
position that they contain such ore deposits.” But in the writer’s 
none where the extreme temperature was over 1,000° F., an 
_ possibly little short of that of fusion, where, consequently, what- 
¢ver material was movable by means of vapor or otherwise, would 
Tocks, and the concentration and distribution of the ores; chief 
