A. C. Lawson—Geology of the Rainy Lake Region. 475 
we have any cognizance. If, however, we inquire as to the 
age of these rocks we are forced by the direct application of 
the simplest principles of geological science to look upon them 
as of later age than certain of the series which overlie them. 
We do not yet know their original condition prior to the fusion 
from which they solidified into granites, syenites and gneisses. 
They may have been sedimentary ; they may have ‘been the 
original crust of the earth. The abstract speculations that are 
so often indulged in on this and similar questions have not 
decided the facts of the matter. There is as yet no sufficient 
ground for a just opinion upon it. But whatever may have 
been that original condition the evidence is clear on this point, 
viz: that the fusion and solidification, whereby they were 
brought into their present condition as firm crystalline rocks, 
took place at a period subsequeat to the existence, in a hard, 
brittle condition, of the stratiform and often very distinctly 
clastic rocks which occupy a higher place in the column. 
Therefore, as rocks, the members of this fundamental system 
are of younger age than that of the nearest overlying forma- 
tions. An analogous case with which every geologist is 
familiar is that of dykes. These are of younger age than the 
strata they cut, although the main mass, of which they are 
merely the apophyses, is far inferior to those strata and may 
form the base upon which they rest. These apparently para- 
doxical but naturally quite consistent attributes of absolute infe- 
riority of position with reference to all observable stratiform 
systems or series, and an age younger than part of the latter, 
places a classification of these Archean formations based on 
age at variance with that which has reference to stratigraphical 
position. This is not usual in geology,except in the case of 
intrusive sheets of trap, and raises the question of which 
method should be adopted. The classification according, to 
age is the usual one, but although this is facilitated in the post- 
Archean formations by a knowledge of the laws governing 
the distribution in time of organic forms, it is primarily based 
upon the relative position of strata. The most prominent idea 
associated with these granites and syenites and their gneissic 
modifications is their basal or fundamental relation to all strati- 
form rocks. The formations of the region are, therefore, con- 
sidered in their natural ascending order, in so far as they are 
stratiform, while dykes and intrusive bosses are taken in order 
of their age. 
Tbe group of rocks comprised in the table given above is 
designated geologically as the Laurentian System in accord- 
ance with the practice in vogue among geologists of so naming 
the lowest well-defined system of crystalline rocks which is 
clearly separable from overlying strata. It is not intended by 
