Book Notices. 199 



many other points. Several smaller rivers also occupy similar depres- 

 sions, " The detailed examination of the region, however, amply 

 demonstrates that the sculpturing to which the surface owes its present 

 configuration was practically completed long before the advent of the 

 glacial epoch, and tliat the main valleys, especially those of the Ottawa 

 ■and Mattawa Rivers, were in existence long prior to the deposition of 

 the Palaeozoic sediments." ^Vith the exception of some comparatively 

 small areas occupied Ly Palaeozoic outliers, ranging in age from Black 

 River to Niagara, the district is underlain by rocks of Laurentian and 

 Huronian Age. The Laurentian, with the exception of a few small 

 ■occurrences, is represented exclusively by the Fundamental Gneiss, a 

 mass of granitic and dioritic rocks, usually possessing a foliated struc- 

 ture in which are many streaks, bands or inclusions of basic character, 

 allied to diorites or diabases in composition, and representing either 

 basic segregations from the granitic magma or portions of basic intru- 

 .sions caught up in it. This Fundamental Gneiss, it is believed, 

 ijirobably represents the original crust of the earth, which has under- 

 ;gone successive fusions and re-cementations before reaching its present 

 ■condition. In placing these rocks at the base of the series it is not 

 intended to assert that they stand for any distinct or prolonged period 

 •of geological time, nor to affirm that these rocks in their present con- 

 dition and with the foliation which they now possess antedate those of 

 the Huronian System. This, as is shown, is not the case in many, or 

 even probably in most instances. 



The chemical and mineralogical composition of the gneisses as well 

 as the character and origin of tlieir foliation and the genetic relation 

 of their associated pegmatites are considered at length and many inter- 

 esting facts brought forward whicli cannot here be further discussed. 



The Grenville Series, so extensively developed further south, is in 

 this northern area represented only Ijy a few very small and unimport- 

 ant occurrences of highly crystalline limestone and a single occurrence 

 of gneiss. They occur isolated from one another and surrounded by 

 Fundamental Gneiss on every side, and are referred to the Grenville 

 Series on account of their identity in petrographical character with the 

 areas of this formation immediately to the south. 



The district also includes large tracts of country underlain by pyro- 

 clastic and epiclastic rocks, forming a north-easterly extension of the 

 development of the " typical " Huronian area on the north shore of 

 Lake Huron. At one place on Lake Temiscaming these Huronian 

 I'ocks are found resting upon the floor of Fundamental Gneiss on which 

 they were originally deposited, and of whose detritus they are made up 

 — ^everywhere else the Fundamental Gneiss has been refused or softened 

 and penetrates the superincumbent Huronian. The total thickness of 

 the Huronian in the area is about eighteen hundred feet, made up as 

 follows : 1. Breccia-conglomerate, 600 feet. 2. Shales and slatygrey- 

 ■wackes, 100 feet. 3. Quartzose grit or Arkose, 1100 feet. Associated 



