214 TJic American Geologist. April, isos 
granetised mica schists, folded to the highest degree. There 
are also typical mica schists, and, in the granites, inclusions of 
dioryte and peridotyte. 
All these rocks appear at the south of the city of Tammer- 
fors in a belt, sometimes having the width of 40-60 kilometres, 
extending toward the west to the gulf of Bothnia, and toward 
the east beyond the lake Paijanne. The same formation 
is also very extensive in other parts of the country. 
To the north from this belt of strongly metamorphic rocks 
come in the schists of Tammerfors, or Bothnian formations. 
They are in bands extending from west to east and generally 
following the borders of the gneiss formation and the great 
area of post-Bothnian granite which extends from the gneisses 
toward the north covering an area of more than 23,000 square 
kilometres . The layers of these schists are always nearly 
vertical. 
These schists are remarkable for their character, which is 
at once crystalline and completely detrital. They are often 
represented by typical phyllytes which sometimes approach 
argillytes and sometimes pass into fine-grained mica schists, 
often containing feldspar. In this case they present a gneissic 
character. 
The phyllytes of Nasijarvi shows by their very distinct 
stratification and their internal structure, that they are a for- 
mation of shale in a metamorphic state, intercalated with thin 
beds ol an argillaceous sandstone (leptitic phyllyte). The 
phyllytes often contain a carbonaceous substance, sometimes 
accumulated in thin bands, the outlines of which suggest an 
organic origin. 
A very typical leptyte, of a reddish color and poor in 
mica (always black mica), appears in a small area west from 
Tammerfors. It shows a distinct alternation of beds orig- 
inally horizontal, and of layers which possess an oblique strati- 
fication. 
Dark green schists, rich in amphibole (and most frequent- 
ly in uralite), and in plagioclase which constitutes porphyritic 
crystals, are almost as widely extended as the phyllytes. These 
rocks, called porphyroids, are metamorphic tuffs of Archean 
effusive rocks. In them are sometimes seen intercalated beds 
of true eruptive rocks, notably uralite porphyrytes and plagio- 
