CHAPTER II. 
GEOLOGY. 
Section A.—GEOLOGICAL FORMATION. 
Or the geological formations of Finland Dr Ignatius 
writes:— They carry us back to the primitive geological 
epochs. They are composed in great part of crystalline 
rocks covered with a comparatively thin layer of earth of 
the post-tertiary period. With regard to their origin, 
these crystalline rocks are, some of them, schistose and 
metamorphic, the others compact and igneous. These are 
for the most part of the old Taurentian formation. The 
second, having been erupted from subterranean sources, 
have traversed the former, turning them over, and covering 
them in some places over an immense extent of surface. 
It is these igneous rocks also which form the greatest part 
of the mountains of Finland. They are divisible according 
to age, into three principal groups characterised by differ- 
ent granitic formations—granite-gneiss, predominating 
to the south of Salpauselka ; porphyritic-granite, covering 
wide extents, especially in the centre of the country; and 
pegmatite-granite, which, in the form of thin filans (of quartz, 
and of granite, of fine and of coarse grain), are met with 
in all the other rocks, metamorphic and plutonic. Amongst 
the granite-porphyroids may be specified one form which 
the Finnish call Rapakivi, which is well known from the 
facility with which it is crumbled; it is found especially 
to the south of Salpauselk&, in a limited space, bounded 
on the west by a line drawn from Borga to the lake of 
Paijanne, and on the east by the Vuoksi and the 
Aeyrapaanselké, a chain of hills which runs from the 
R 
