REVIEWS 715 
basic intrusions caught up init. This fundamental gneiss, it is believed, 
probably 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 their foliation and the genetic rela- 
tion of their associated pegmatites, are considered at length, and many 
interesting facts brought forward which cannot here be further dis- 
cussed. 
The Grenville series, so extensively developed further south, is in 
this northern area represented only by a few very small and unimportant 
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 
pyroclastic and epiclastic rocks, forming a northeasterly extension of 
the development of the “typical”? Huronian area on the north shore 
of Lake Huron. At one place on Lake Temiscaming, these Huronian 
rocks 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 1800 feet, made up as follows: 1. 
Breccia-Conglomerate, 600 feet. 2. Shales and slaty greywackes, 100 
feet. 3. Quartzose grit or Arkose, 1100 feet. Associated with these 
Huronian sediments are numerous intrusions of gabbro and diabase, 
some of which pass over gradually into flesh-red granites, represent- 
ing, it is believed, portions of one and the same magma. 
No attempt is made in this report to correlate the Grenville series 
and the Huronian of the area, as the facts are insufficient to warrant 
the attempt. And it may be remarked incidentally in this connection 
that a statement, made on page 415 of the current volume of this 
