1 8 Sketch of the Geology of Northern Europe. 



quartz between the felspar, and sometimes 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 vallies, 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 beneatli 

 its own rubbish, " and its ending is unknown." 



Red and grey veined marble, form the deeply indented northern 

 shores of Lake Ladoga. Veins of s'ulphuret of copper, and iron 

 ore have been wrought near its northern boundary, and magnetic 

 sand is obtained from one of its islands. 



Lake Onega is bounded on the northwest by rocks of dark green 

 jasper breccia ; on the north by a gi-een-veined marble full of tremo- 

 lite. It is crystalline and probably a primitive limestone. The west 

 coast consists of a 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 

 amethy,st penetrated with tufts and pencils of oxyd of iron in radiating 

 capillary crystals. At others the quartz is coated witli red and yel- 

 low oxyd of iron, and resembles the hyacinth of Compostella. — 

 Some of the blocks present cavities, each lined with a separate variety, 

 others contain all the varieties in one group." 



The traces of diluvian 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 



