1840.J 595 



occasionally even sharp. Other rounded surfaces are met with in 

 the deep sharp angles of rock, and in recesses where it is not to 

 be conceived that a glacier could have forced its way, and produced 

 this effect, leaving the inner sides of these recesses unworn by 

 friction and their edges angular. In some of these cases the 

 rounding of the narrow parts is perfect, and they are occasionally 

 even fluted in a manner identical with that of other flutings in 

 the exposed and open parts of the rock. 



The author then refers to another example of i-ounded, grooved, 

 and striated rocks seen in the valley of the Ogwyn near the bridge, 

 where the river as it issues from the lake forms a cascade at a spot 

 close to the high road. The rounded rocks here are described as 

 weathered ; but " quartz veins which traverse the masses, and pro- 

 ject two inches above the surface, are polished and rounded on the 

 edges ; " and in this group of rounded, dome-shaped bosses, some 

 of the surfaces are fluted, the furrows being regularly parallel and 

 equidistant, and as nearly as possible of the same width and depth. 



At first sight the appearance here presented seems to be refer- 

 able to glacial action ; but the author observed that the direction 

 of the flutings is opposed to that of the valley ; that the striaa or 

 furrows which are not parallel are likewise not in the direction of 

 the line of the valley, but range at all points of the compass, many 

 of them crossing one another irregularly, and others having a 

 radiated appearance, and that in the midst of the parallel furrows 

 on the rounded smooth faces of rock are projecting portions of the 

 same rock, some of them rounded, fluted, and striated at the tops, 

 but angular at the edges, and not rubbed at the sides, while 

 smaller portions, scarcely an inch thick, stand fully exposed in the 

 line of descent which a glacier must have taken, presenting the 

 appearance of thin portions of schist full two feet in height, and 

 almost as much in breadth, perfectly unaltered. Although the 

 rounding of the general surface has taken place on each side of 

 them, the flutings are in absolute contact with them, and there 

 are stri» between and even upon them. It seems clear, that had 

 the rounding of the rock been effected by the passage of a glacier, 

 these fragments must necessarily have been swept away, and thus 

 the rounding of the rocks must be due to some other process. 



It is the opinion of the author that this rounding took place 

 beneath the sea, and that the i-epeated undulations of the strata 

 parallel to the principal mountain chain in the district, forming a 

 succession of anticlinal and synclinal axes, have been the original 

 cause of the formation of the oblong bosses and rounded rocks, 

 while the fracture of the beds has produced the furrowed appear- 

 ance. It is also suggested as explanatory of this view that, at the 

 time of the disturbances which produced these undulations, the 

 rocks may have been only partly consolidated, and that thus the 

 long parallel lines at first produced might readily be acted on by 

 the marine currents, which were sufficiently powerful to clear off 

 the sharp edges, but not to remove the projecting quartz veins. 

 The author concludes this part of his memoir by stating his 



VOL. IV. PART lU. y Y 



