514 
STRIATION AND POLISH OF ROCKS IN LAKE ONEGA. 
flat, with no eminences to catch the drift, which however transported, has passed 
on southwards till arrested by other heights 1 . 
Very different is the surface of the Carelian country to the north of Olonetz, and 
which lies between the lakes Onega and Ladoga. Here again we found ourselves 
in precisely the same sort of tract as that on the edges of Finland north of St. Pe- 
tersburg. Undulating hillocks, or rather ridges, 200 or 300 feet in height, trending 
foi the most part from north to south, or north-north- west to south-south-east, 
succeed each other in rapid succession, and are from top to bottom composed of 
granitic and northern detritus, often separated from each other by small lakes. 
We were, in fact, on the ancient shore of the great Scandinavian chain, and amidst 
bands of its granitic detritus, much resembling that to which we shall afterwards 
allude as covering many parts of Sweden 2 . 
The point we most wished to ascertain was, if the crystalline and hard rocks 
which rise to the surface immediately to the north of Petrozavodsk, and over 
which the vast mounds and ridges of detritus to the south of it had passed, exhi- 
bited the phenomenon of polished and scratched surfaces, and if these scratches 
were in the chief direction of the drift. 
On this point we soon satisfied ourselves, by boating up the Lake Onega to the 
northern extremity of the little bay or strait of Salomi, where we found the hard 
eruptive greenstone and associated breccia (Salomenski-kamen, see p. 18) per- 
fectly rounded off and grooved on the northern face of a small promontory opposite 
to the church, with innumerable small strise having the direction of magnetic north 
and south. As the water of the lake which washes round this small headland was 
very transparent, we could observe the striae down the northern slope of the rock 
1 Being tired with the continuous expanse of sands which here cover the lowest Silurian clay, we be- 
came very impatient to discover some rock in situ, and determined to ascend the banks of the river Oyat 
for that purpose. As soon, however, as the peasants had prepared our equipage, it was quite evident that 
our search would be fruitless, for not one of the horses was shod ; an economy very generally practised in 
Russia, where no hard ground or rock is at the surface. We had, in fact, been led to this excursion by 
our constant inquiry after stones ; and the Russian peasants, who are invariably well acquainted with 
every natural feature in their neighbourhood, dragged us through sandy forests for many miles, until they 
truly pointed out a few northern blocks, the only stones, in fact, of the whole tract. 
• At Petrozavodsk there seemed to be some means of separating this coarse and ancient drift, which 
contains boulders and is covered by them, from certain overlying sands, which having filled depressions 
in the drift clay, have since been excavated ; but we had not time satisfactorily to work out this question 
Other peculiar phenomena, caused by the melting and bursting of the ice of the lake Onega near Petro- 
zavodsk, will be described in the next chapter. 
