84 BIBLIOGRAPHY AND INDEX OF N. A. GEOLOGY, [bull. 146. 
552 Winchell (N. II.). The eruptive epochs of the Taconic or Lower 
Cambrian. 
Am. GooL, vol. xv, pp. 295-304. 
Describes the differences between the Archean complex and the erup- 
tive rocks associated with the Cambrian in North America. Discusses 
the relations and succession of the Cambrian rocks of western New 
England, eastern New York, and the evidences as to the age of the 
Adirondack gabbros. Reviews the recent opinions as to the succession 
of the Adirondack rocks. 
553 Canadian localities of the Taconic eruptives. 
Am. Geol., vol. xv, pp. 356-363. 
Reviews the descriptions and classifications of the Huronian and Que- 
bec groups in Canada by Logan, Selwyn, Ells, and Dawson, and discusses 
the relations of these sedimentary and igneous rocks. 
554 Steps of j)rogressive research in the geology the Lake 
Superior region prior to the late Wisconsin survey. 
Am. Geol., vol. xvi, pp. 12-20. 
Reviews the descriptions of the Huronian rocks of Lake Superior by 
Canadian geologists, a report by Foster and Whitney on the geology of 
the Lake Superior district, and reports by Brooks, Pumpelly, and 
Rominger on the copper-bearing rocks. Gives a summary of the author's 
views regarding the state of opinion on the geological questions under 
consideration up to the time of the Wisconsin survey. 
555 The Keweenawan according to the Wisconsin geologists. 
Am. Geol., vol. xvi, pp. 75-86. 
Discusses the conclusions of the geologists of the Wisconsin survey 
from 1873 to 1879 concerning the Laurentian, Huronian, and Keweenawan 
rocks of the Lake Superior region, and also the published opinions of 
Irving and Van Hise. 
556 A rational view of the Keweenawan. 
Am. Geol., vol. xvi, pp. 150-162. 
States several objections to separating the horizontal Lake Superior 
saudstones from the tilted sandstones, and discusses the evidences in 
support of the several statements. Discusses the evidence as to the age 
of the eruptive rocks which have been included in the Keweenawan 
series. 
557 The synchronism of the Lake Superior region with other por- 
tions of the North American continent. 
Am. Geol., vol. xvi, pp. 205-213. 
Compares the succession of geologic events in the Lake Superior 
region with that in eastern New York, and explains the accompanying 
map of the Lake Superior region. 
558 The latest eruptives of the Lake Superior region. 
Am. Geol., vol. xvi, pp. 269-274. 
Describes the synclinorium of the Lake Superior region, and discusses 
the relations of certain eruptives and the evidences indicating that the 
Black Bay sandstones are a part of the Keweenawan. 
