FORCHHAMMER ON THE BOULDER FORMATION. 375 



the other. In these points there seems no essential difference 

 between the Scandinavian and the Swiss phenomena, but it ap- 

 pears to me as if the regularity in the boundary of the rocks thus 

 acted upon, at least so far as regards the extent of this regularity, 

 is peculiar to Scandinavia. The one side of the scratched rocks 

 (called by Sefstrom the lee-side) is here always more or less de- 

 cidedly perpendicular, while the other (the stoss~seite of that geo- 

 logist, a phrase intimating that this side has been exposed to the 

 pushing forward of the drift) is always a very gradual incline. * 

 The perpendicular side of the scratched rocks is at right angles 

 to the direction of the scratches. 



If now we suppose, as is most probable, that the material of 

 which the Aosar are made up, consists of the fragments broken 

 off from the rocks now scratched and furrowed, it is not easy to 

 imagine how a flood powerful enough to tear away with such ex- 

 treme violence so large a quantity of rock, could at the same time 

 deposit the broken fragments amongst the very rocks destroyed. 

 But the Aosar are, in point of fact, not at all rare in the neigh- 

 bourhood of scratched rocks, upon which indeed Sefstrom himself 

 has found these heaps ; and if it should be suggested that some- 

 times, under the shelter of a hard rock, they might occasionally be 

 deposited, it must be remembered that they are in fact far too widely 

 extended throughout Sweden for such an explanation to suffice. 

 This very circumstance shows that the cause of the scratching of 

 the rocks and the deposit of hillocks of gravel and sand cannot 

 have been universal, but must have been, on the other hand, the 

 result of innumerable separate disturbances. Sefstrom assumes 

 that the course of his great flood of erratic blocks was from north 

 to south, his proof of this resting partly on the relations of the 

 stoss- and lee-side, and partly on the relations of the so-called normal 

 and abnormal, principal and collateral scratches ; but it seems to 

 me that this proof is imperfect, and that the phenomena are not 

 fairly judged of, since according to this idea the normal striae 

 should only be sought for on the highest of the Norwegian moun- 

 tains ; and unless we admit that the side towards the north has 

 been denuded of many feet, nay of many fathoms, of rock, we 

 cannot make it appear probable that the movement of the flood 

 was not directly opposite to that north to south direction assumed. 



In approaching the Swedish coast of the Cattegat from the sea, 

 we at first only observe, as it were, pinnacles of rock rising above 

 the waves. As we advance towards the land, however, small 

 islands appear, and these become larger and more numerous near 

 shore, their vertical side being seaward. Now to me these islands 

 present a perfect analogy with the intersected and furrowed rocks 



* Sefstrom must, it would seem, imagine that the country was originally every- 

 where terminated by a perpendicular cliff, (now the lee-side,) while the stony 

 flood has cut off on the other side every sharp projection, leaving them on the 

 lee-side unaltered. But it is hardly to he believed that any kind of temporary 

 deluge can have cut off such enormous slices from a rock so hard. 



B b 4 



