16 LOWEST SILURIAN ARKOSE FORMED FROM PRE-EXISTING GNEISS. 
ceratites), and passing over the beds of alum-slate and black limestone (Z>), with 
their Trinuclei, Paradoxides or Olenus, Agnosti, &c., the fucoid sandstone (a) is 
there seen in horizontal masses, perfectly conformable to all the overlying strata, 
and distinctly superposed to the gneiss below (o). For, though the absolute junc- 
tion of the sandstone and gneiss is not seen, the two rocks are within a hundred 
paces of each other, and without the slightest indication of any other substance 
between them. Now the gneiss is here not merely in a lower position than the 
contiguous sandstone, hut, besides its crystalline structure, is at once seen to 
belong to rocks of an entirely different class, and to be quite independent of the 
overlying Silurian formation. In short, the one must have assumed its direction 
and structure before the other was accumulated. Denuded in large rounded pro- 
tuberant bosses, the gneiss, as laid bare in numerous places, consists of fine alter- 
nating layers of felspathic and quartzose, black, white and pink colours, which 
having a strike that varies from magnetic north and south to north-west and 
south-east, are either vertical, or dip at angles of 70° and 80° to the east or west. 
In offering the above woodcut to explain these relations, we apprehend that we 
have already said enough to convince our readers, that the gneiss, including many 
varieties to which it is not now our intention to allude, must be considered the fun- 
damental rock of Sweden, which existed and was even highly inclined, contorted 
and crystallized before the very lowest Silurian beds began to be formed. 
But if, after examining the section of Kinnekulle, we could have entertained any 
doubt on this point, it would have been dispelled by what we saw in other locali- 
ties, where the lowest of the Silurian or protozoic strata are not only absolutely 
superimposed on the granitic gneiss, but are proved to have been derived from it, 
and composed of its very materials, We saw the first example of this phsenomenon 
at Lugnos, near the northern end of the Billingen Hills, where the Lower Silurian 
beds (as at Kinnekulle), being deprived of their cover of basalt, which has pro- 
tected them from denudation over a considerable area to the south, are worn down, 
so as only to exhibit their lowest portion, the alum-slate (&) being partially visible 
above the slopes of the rising ground, and the fucoid sandstone («) lying beneath 
it, as expressed in this section. 
LUGNOS. iii- 
S. Erratic Blocks. 
