2i6 The Autcrican Gcoloi^isf, April, i>os 
Hormistonlahti, the total thickness of the formation of the 
schists of Tammerfors is at least from four to five thousand, 
metres (2,000 metres of phyllytes, 1,500 metres of the lower 
tuffs, and of the conglomeratic zone, and the remainder upper 
tuffs, with their intercalations of phyllyte and conglomerate). 
The order of this enumeration is also that of their stratigraphic 
succession, the phyllyte always outcropping alongside of the 
gneisses which supported it formerly, and these last south of 
the schists. 
The great contrast between the straight stratification of 
the phyllytes and the intense folding of the gneiss warrants the 
presumption of a great hiatus between these formations. In- 
deed, at several points, as at the north of Aittolahti, can be 
seen dikes of granite which are abundant in the gneiss, which 
never cross the phyllytes. There can be seen, in the neighbor- 
hood of the contact line, only small masses of porphyritic 
granite introduced in a solid state during the folding of the 
phyllytes, but never anything that can be interpreted as an 
injection of this rock when in the condition of a magma. 
In the region to the east from Nasijiirvi, north from Siuro 
and in the country west of Piiijanne, can be seen the clear con- 
tact between the phyllytes and the porphyroidal granite. It is 
there easy to see that the granite has served as a base for the 
metamorphosed sediments which constitute the formation of 
the schists of Tammerfors. 
The granite which outcrops north of the schists shows al- 
ways contact phenomena that indicate its more recent date. 
It cuts the schists in numerous dikes, and the manner of pen- 
etration is so intimate that over several hundreds of^metres the 
contact rock can be called gneiss in the form of dikes or gran- 
itized schist. One can very easily study the origination of 
such a rock on the west shore of the Nasijarvi, at the northern 
contact of the outcrop of the schists of Tammerfors. On the 
eastern shore, where can be seen analogous phenomena, the 
porphyroid, rich in uralite, appears to be converted into a 
massive rock resembling a dioryte. In another contact zone, 
at Orihvesi, the schists are changed, for a distance of more 
than a kilometre from the line of contact, into a schistose rock 
resembling a leptynyte rich in feldspar, which appears to have 
crystallized under the influence of the surrounding granite. 
