18 Sketch of the Geology of Northern Europe. 
quartz between the felspar, and something disseminated through it 
in black spots. The felspar is variously colored ; dark red, pale pink, 
flesh colored, and white, and ash colored. This granite is extremely 
liable to decomposition, and holes are seen in the rocks, of twelve 
and fifteen feet in diameter. In the bottom of some of the valleys, in 
this vicinity, a purplish clay is found, formed probably, by the de- 
composition of the felspar, so abundant in this granite. ‘Towards the 
south the granite recedes beneath the surface, and is lost beneath its 
own rubbish, “and its ending is unknown.’ 
Red and grey veined marble, form the deeply indented northern 
shores of Lake Ladoga. Veins of sulphuret of copper, and iron 
ore have been wrought near its nofthern boundary, and magnetic 
sand is obtained from one of its islands. ia 
Lake Onega is bounded on the northwest by rocks of dark green 
jasper breccia; on the north by a green-veined marble full of tremo- 
lite. It is crystalline and probably a primitive limestone. The west 
coast consists of red sandstone of great hardness. Bowlders of 
this sandstone are found far south, distributed over a large tract of 
country. ‘The resemblance of the shores of the two lakes, and of 
the gulf of Finland, is peculiarly striking. The northern shores are 
of the older rocks, much broken, the waters deep, and many islands 
skirt the coasts. ‘‘ Sand or sandstone forms the east and west sides, 
and the southern boundary of each is a marsh, behind which at a 
short distance, is a range of secondary limestone hills, of one and 
the same formation.” In the north east part of Lake Onega is the 
celebrated isle of Wolves, famous for its beautiful minerals. Masses 
of dark brown argillaceous iron stone lie loose upon the surface, 
which being broken, discover cavities lined with the most brilliant 
quartz crystals, and oxyd of iron. “Sometimes the quartz becomes 
amethyst penetrated with tufts and pencils of oxyd of iron in radiating 
capillary crystals, At others the quartz is coated with red and yel- 
low oxyd of iron, and resembles the hyacinth of Compostella.— 
Some of the blocks present cavities, each lined with a separate varie- 
ty, others contain all the varieties in one group.” ' 
The traces of diluvan action, and the course of the currents from 
north to south, throughout the whole of Finland are astonishing. 
Without stopping to notice “the stupendous size, and extensive dis- 
tribution of primitive bowlders, it is impossible not to perceive that 
the top of every rock in situ, every tor, every hill and knoll of gran- 
ite, or primitive rock, from Carelia to the Gulf of Bothnia, presents 
é 
Pe tet pre ee ane ee ee SS 
