1845.] 621 



In respect to the close parallelism of the different sedimentary 

 masses of the two continents, I must refer to my opinions and 

 those of my coadjutors in our forthcoming work, and will now 

 merely say that as the succession in N. America has had its base 

 line defined for about 2000 miles, so do the observations of myself 

 and friends apply in the same general manner to an extent not far 

 short of that space, or from the western headlands of Norway to 

 those which separate the White Sea from the glacial ocean. 



In Sweden, as has been shown, the absolute junction of the 

 lower Silurian strata with the pre-existing crystalline rocks, is 

 quite as clear as it can be in any part of N. America, but it is 

 not so in Finland or Russia, where two powerful causes prevent 

 our making the necessary observations. The first of these is the 

 protrusion of much eruptive matter, and the consequent metamor- 

 phism of the conterminous strata ; the other the prodigious accu- 

 mulations of erratic blocks and detritus which obscure the funda- 

 mental rocks. It is not my intention to enter on this occasion into 

 any details respecting either of these operations, which are treated 

 of elsewhere, but merely to call attention to some great physical 

 features along this frontier line, and to explain the probable causes 

 of their production. 



On inspecting the geological map of Russia, which is now pub- 

 lished, it will be seen that, excluding the Gulf of Bothnia, the 

 frontier line, of which I am now speaking, is marked by a great 

 line of waters from S. W. to N.E. The Gulf of Finland is, in 

 truth, but the north-eastern prolongation of the Baltic, and the 

 White Sea is the nortli-eastern termination of this great and ex- 

 tended line of fissure ; whilst intermediate between these two 

 marine gulfs, lie the enormous freshwater lakes of Ladoga and 

 Onega. On further inspecting the map, we are struck with the fact 

 that the longer axis of each of these two great freshwater lakes is at 

 right angles to the main direction of the rocks, and of the White 

 Sea and Finland Gulf; and, further, that a multitude, we may 

 say thousands of minor lakes in Finland, Carelia, and Lapland, 

 are parallel to the great lakes, and also, consequently, transverse 

 to the general bearing of the sedimentary masses in their relation 

 to the subjacent crystalline rocks. Pursuing the inquiry, we see 

 that other gulfs, some occupied by salt-water, as that of Riga in 

 the Baltic, and those of Onega, Kandalaska, and Archangel in the 

 White Sea, are also transverse in the same sense. 



Let us then inquire if the structure and geological phenomena 

 of the region will help us to explain such geographical outlines. 



In a former communication I briefly pointed out the chief 

 relations of the rocks on the banks of the great lake Onega, and 

 showed, that wherever the eruptive matter (whether in the form of 

 greenstone, syenite, or trappean conglomerate) had come to the 

 surface, it had formed bands parallel to the great lake Onega, and 

 that in the vicinity of such eruptions Silurian limestones had 

 been metamorphosed into marble, and soft sandstones (which 

 at some distance from the eruptions contained Devonian fossils) 



