474. A. C. Lawson—Geology of the Rainy Lake Region. 
type. But what this geographical separation means, whether 
the one is earlier or later than, above or below, the other, or 
what other geognostical relation exists between them, either in 
space or in time, the meagre amount of field work that has yet 
been done, relatively to the magnitude of the units with which 
we have to deal, leaves still an unsettled question. Such feeble 
suggestions of possible relations as have been received will be 
set forth in another place. 
The granites and the foliated rocks of similar composition and 
habit, which are classed with them in parallel series, are gen- 
etically the same, the latter owing their distinctive characters 
to a differentiation in structure due to the influence of certain 
conditions affecting portions of ‘a more or less homogeneous 
magmatic mass at the time of its solidification. The field evi- 
dence establishing the common genesis of the granite and 
gneiss is so strong that there is no room for doubt in the mat- 
ter to one who has carefully studied their occurrence in nature. 
It is of course possible for geologists who are wedded to 
extreme metamorphic views to regard these rocks, even grant- 
ing their sometime magmatic condition, as fused sedimentary 
strata; and they are at perfect liberty to do so, but so far as 
evidence goes the supposition is purely gratuitous and cannot 
in the absence of facts to support it be entertainted as a very 
probable hypothesis. The evidence in favor of such a supposi- 
tion is, so far as can be gathered from a study of the region 
under consideration, very speculative. What is said of the 
granites and granite gneisses is also true of the syenites and their 
foliated varieties. The identity and igneous origin of the 
foliated and non-foliated series is shown by (1) the direct trace- 
able passage from the granitic to the gneissic phase in a rock 
mass which must be regarded as a geological unit; (2) by the 
identical nature of their contact relations to other series of 
rocks to be mentioned, viz: the igneous, brecciated nature of 
the contact, the gneiss or granite holding angular fragments of 
the rock through which it breaks, and sending apophyses into 
it, which, where the rock is gneissic are often distinctly foli- 
ated ; (3) the identity, as revealed by the microscope, of the min- 
eral composition and structure of two varieties of the same 
mass. 
This group of crystalline rocks, granites and syenites, foll- 
ated and non-foliated, forms the floor of the region upon which 
rest all other formations that are not in the condition of dykes 
or intrusive bosses. Regarded as a geological system of rocks 
it occupies an apparently paradoxical and anomalous place in 
any scheme of classification. As the floor or basis upon which 
the geological column of stratiform rocks rests it must be 
regarded as the first or fundamental system of rocks of which 
