372 REVIEWS 
indicating that pneumatolitic action was an important agency in their 
origin. The fissure deposits are associated with the complementary 
dikes and contemporaneous or slightly later quartz veins, and include 
replacement deposits in the wall rock. They occur principally in the 
granodiorite. The fissures have a steep southerly dip. 
The post-Miocene deposits are argentiferous gold ores. They 
occur in quartz-adularia fissure veins in the old rhyolite in the Jarbidge 
district. They were discovered late in 1909. ‘The fissures are mostly 
contained in two main systems which converge downward. Those of the 
west system dip steeply to the east and those of the east system dip 
steeply to the west. The gangue is pseudomorphic after calcite and 
rhyolite and was deposited by ascending thermal solutions that dis- 
solved out and replaced the earlier calcite gangue. 
Sandstone of the Wisconsin Coast of Lake Superior. By FREDERIK 
TURVILLE THWAITES. Bull. No. XXV, Wisconsin Geol. and 
Nat. Hist. Surv. Pp. 117-+vii. Plates XXIII. Madison, 
IQI2. 
The stratigraphic relations and geologic age of the red sandstones of the 
Lake Superior region have long been a subject of discussion arising from 
the fact that the older sandstones are closely allied to the Keweenawan 
while the younger beds partake more of the general characteristics of 
the Cambrian. The older sandstones are characteristically composed 
of arkose material and the strata are nearly always tilted. The younger 
group is almost wholly quartz sandstone, and its beds are generally hori- 
zontal. Both series, so far as known, are entirely devoid of organic 
remains. Former investigators recognized that the lower group was a 
part of the Keweenawan series, but opinions differed as to its relation 
to the upper; some held that the two were conformable, while others 
maintained that an unconformity existed and that the upper group 
probably corresponded to the Cambrian of southern Wisconsin, or its 
conformable downward extension. 
One of the principal results of the present study was the conclusion 
that the upper quartz sandstone grades conformably downward into red 
shales and arkose sandstones which possess the same characters as the 
main body of the recognized Keweenawan sediments. As no conclusive 
evidence was discovered which tended to indicate that the two groups 
are unconformable, the facts are believed to warrant the belief that the 
sandstones form a single essentially conformable series. What has 
