314 A. E. BARLOW — LAURENTIAN AND HURONION ROCKS. 



Pag 



Broder Township 322 



Direction and Extent of the Contacl 322 



Microscopic Examination of I [uronian Schist 322 



Microscopic Examination of the < hieiss 323 



Character of the I tucks near the Line of ( lontact 321 I 



Dell Township, I >aisy and Baby Lakes and Lake Alice 32-J 



Direction and Extent of the ( !ontact 324 



Microscopic Examination of foliated < rneiss - 324 



Daisy Lake Rucks 324 



Microscopic Examination of the Quartzite 324 



Rocks between I >aisy and Baby Lakes 325 



Microscopic Examination of Contact Rock 325 



Rooks between Baby and Alice Lakes 325 



Wahnapital River 326 



Contact indicated by ( lharacter of Rocks 326 



The Huronian Representative 326 



Rocks of the Contact between ('artier and Straight Lake Stations 327 



Two Islands near Thessali >n 327 



Contact previously described by < )thers 327 



Difference in the Conclusions of the Author and other Writers recited. 327 



( (inclusions and Facts supporting them 330 



Introduction. 



In this paper, which is a revision and extension of one published in 

 the American Geologist of July, 1890, the writer proposes to bring 

 forward some observations on the nature of the contact between the 

 Huronian rocks of Lake Huron, described by Logan and Murray, and 

 the Laurentian gneisses, which it is thought have an important bearing 

 on the question of the origin and relative age of the latter. 



THE HURONIAN JR OCA'S. 



The rocks of the Huronian area to the north of Lake Huron are made 

 up of a series of quartzites, graywackes, slate conglomerates, day slates 

 bydromica, chloritic, and hornblendic schists, greenstones and some 

 bands of cherty limestones or dolomites. Frequently these rocks show a 

 pyroclastic origin, and tuffs and breccias arc very commonly met with. 

 The majority of the clay slates have the appearance of being very little 

 altered, except in contact with the greenstone and other igneous rocks, 

 and present in greal part the same appearance as when hardened from 

 the original soft sediments. The quartzites, graywackes and slate con- 



