INTRUSIVE ROCKS AND ALTERED PALAEOZOIC STRATA. 
22 * 
not rise more than from sixty to eighty feet above the sea, and is about three miles 
in circumference. It is entirely composed of granitic gneiss, which is regularly 
bedded. The strata are vertical, and have a strike north-north-west, to south- 
south-east {magnetic), with many joints, the most dominant of which are also 
vertical and cut the strata obliquely, passing from north-east to south-west. The 
surface of the rock being generally laid bare, the different, vertical beds are well- 
exposed. Among several varieties, some contain much black mica and quartz, 
others hornblende, quartz and felspar, with a little mica ; and in a third, still more 
quartzose, are certain micaceous beds charged with garnets, occasionally of con- 
siderable size. Quartz veins are apparent here and there, but in our short exami- 
nation we did not observe any signs of true granitic or other intrusive rock. This 
isle is chiefly interesting as being the most southerly point (at the mouth of the 
river Onega) to which the crystalline rocks of Lapland advance in that parallel of 
latitude ’. Other islands of similar composition are dotted about the bay, to the 
north of Ki-Ostrof, and one of these, celebrated as the site of a great monastery 
the resort of many pilgrims, is called Solivetsk. 
But, though not seen by us in these north-eastern isles or promontories, various 
rocks of intrusive character have been already mentioned as associated with the 
azoic or crystalline rocks of Scandinavia, from whence they continue through Fin- 
and into Lapland and the northern tracts of Russia (see Map). The same sort of 
co ocation exists in Finland and Lapland, where the late M. Bohtlingk has recently 
° servec , in numerous instances, that the greenstones have been injected into the 
surrounding crystalline masses 8 . 
ntrusive Rocks and Metamorphosed Palaeozoic Strata . — Passing from the con- 
eration of the older crystalline rocks, and those which we had no opportunity 
f distinguishing from them, we would now briefly advert to masses that are cer- 
tainly of posterior age. In the region under our review, we purposely examined 
the central and northern parts of the Lake Onega and its western bank, where 
^appean rocks occupy a large portion of the surface. Referring our readers who 
. M ' tlohdmgk, in a recent journey round the northern shores of the White Sea, has shown the exten- 
sion of hard sandstone and other rocks on the northern shores of the White Sea (as we have laid it down 
lU the Map )’ but the S reat mas® and nucleus of the country, as in Scandinavia, is made up of gneiss and 
granite, with greenstone — Acad. Petro. Bull. Sclent., vol. vii. 
See Bulletin Scientifique de l’Academie Imper,, vol. vii. p. 194 . 
