370 REVIEWS 
Preliminary Report on the Copper-bearing Rocks of Douglas County, 
Wisconsin. By ULyssks SHERMAN Grant, Ph.D. Wisconsin 
Geological and Natural History Survey, Bulletin No. VI. 
Economic Series No. 3, pp. 55. 1900. 
The report is the result of field work during the summer of 1899, 
and deals in a preliminary way with the St. Croix and Douglas copper 
ranges of Douglas county, Wisconsin. It contains four geological 
maps and several illustrative plates. Chapter 1 outlines the geology 
of the county and contains a sketch of the three rock series repre- 
sented; namely, the Cambrian, the Upper Keweenawan, and the 
Lower Keweenawan. The Lower Keweenawan consists of igneous 
rocks, largely basic lava flows with a few interbedded conglomerates. 
The copper deposits are usually at or near the contacts of the flows, 
and the author has given some of the characteristics by which the con- 
tacts may be known. The Upper Keweenawan consists of conglomer- 
ates, sandstones and shales, lying apparently conformably upon the 
igneous beds and dipping southeast at low angles. The Lake Superior 
sandstone underlies the northern part of the county, and consists 
essentially of quartz sand, but in some places becomes conglomeratic, 
and in others clayey. or shaly. Its junction with the Lower Kewee- 
nawan is marked by a fault of considerable displacement along which 
the traps are shattered. Chapter 11 describes some of the more impor- 
tant outcrops of the St. Croix range and chapter 111 treats the Doug- 
las range in a similar manner. 
The last chapter is a “brief discussion concerning the mode of 
occurrence of the copper, where to search for copper, and the value of 
the deposits.” ‘This chapter is of special value to the prospector and 
the investor. On pages 53 and 54 are given several analyses of copper- 
bearing rocks from the two ranges. R. D. GEORGE. 
Upper and Lower Huronian in Ontario. By ARTHUR P. COLEMAN. 
Bulletin of the Geological Society of America, Vol. XI, 
pp. 107-114. 1900. 
In his work as geologist for the Ontario Bureau of Mines the author 
has gathered much material bearing on the problem of the Huronian 
in Ontario. In tracing the Michipicoten iron range it was found that 
the band of siliceous rock associated with it, and generally resembling 
