CURRENT PRE-CAMBRIAN LITERATURE 419 



belt comes into contact with the gneiss which prevails to the eastward, 

 it is not always separated from the latter by a very distinct boundary. 

 The rocks in some places pass into each other more or less gradually. 



Barlow and Ferrier 1 discuss the relations and the structure of certain 

 granites and associated arkoses on Lake Temiscaming. An examina- 

 tion of the contact of the granite and arkose shows a gradual and 

 distinct passage of the granite into the arkose. Microscopically also 

 there may be seen evidence of the decomposition of the feldspars of the 

 granite, the breaking up of the feldspar and quartz, and finally the 

 rearrangement and assortment of by water, indicating a gradual transi- 

 tion from the granite to the arkose. 



The arkose is regarded as an Huronian sediment derived from and 

 deposited on the granite. This is regarded as the only instance at 

 present known in which the material composing the Huronian elastics 

 can be clearly and directly traced both macroscopically and micro- 

 scopically, to the original source from which it has been derived. 



Comment. — The final statement is somewhat sweeping. Passing 

 over the numerous instances of clear relations south of Lake Superior, 

 it is necessary only to recall the instances close at hand, at Thessalon 

 and Garden River, described by Irving, Pumpelly, and Van Hise, who 

 found complete evidence of the unconformable relation between the 

 Laurentian and Huronian, and of the derivation of the Huronian 

 sediments from the Laurentian. 



Burwash, 2 during the survey of the boundary line between the 

 districts of Nipissing and Algoma in Canada, takes geological notes 

 of the area traversed. 



The run was made from south to north, from the upper waters of 

 the Vermilion and Wahnipitae rivers, to within thirty-five miles of 

 Lake Abittibi ; and, with the exception of two areas of eruptive granite, 

 the country was found to be underlain for the entire distance by 

 Huronian rocks. The section is given in detail. 



Tyrrell, and Dowling 3 report on the country between Athabasca 



1 On the relations and structure of certain granites and associated arkoses on 

 Lake Temiscaming, Canada, by A. E. Barlow and W. F. Ferrier : Geol. Mag., 

 Vol. V, 1898, pp. 39-41. 



2 Geology of the Nipissing-Algoma line, by Edward M. Burwash : Sixth Rep. 

 of the Bureau of Mines, Ontario, 1897, pp. 167-184. 



3 Report on the country between Athabasca Lake and the Churchill River in 

 Canada, by J. B. Tyrrell, assisted by D. B. Dowling : Ann. Rep. Geol. Surv. of 

 Canada, Vol. VIII, 1897, Part D, pp. 120 with geol. map. 



