On Drift. 7 



when regarded with reference to the whole region, we find them 

 really characterised by the law of divergency. To those observers 

 who had not examined the striae on the shores of the North Sea, 

 some point lying to the north of those shores, and nearly in the 

 direction of Spitzbergen, seemed best to represent the centre of this 

 divergence ; but subsequently M. Bohtlingk observed striae de- 

 scending from Kemi eastward to Onega Bay, on the shores of which 

 it is situated ; and on the northern coast of Lapland he also ob- 

 served them descending from the high lands northward to the sea. 

 These observations have also been corroborated by other observers. 

 Around the district comprising the mountains of Scandinavia striae 

 appear to exist, directed to almost every point of the compass, and 

 the characters of their divergency generally for the whole region 

 may be considered as established. 



The directions in which the detrital matter has moved in its 

 transport across a particuhi locality cannot, of course, be ascer- 

 tained with entirely the sam accuracy as those of the striae ; but 

 the erratic blocks can in numberless instances be identified with 

 the rocks of a particular locality, and thus the mean direction in 

 which a particular block has travelled, can be determined with 

 great accuracy. All the blocks, however, originating in the same 

 locality have not been transported in the same direction. M. Du- 

 rocher has noticed especially a granular granite, easy to be recog- 

 nised, of which the original site is in the department of Vibourg in 

 Finland. The extreme directions in which the blocks have proceeded 

 from this spot comprise an angle nearly equal to two right angles. 

 The mean direction, however, of these blocks, and that along which, 

 or nearly so, the greatest number have proceeded, is very approxi- 

 mately coincident with the directions of the striae along the same 

 line. A similar law holds with respect to other blocks which can 

 be traced to their respective original sites. It may, therefore, be 

 asserted as a law in this region, that the general or mean direc- 

 tions of transport are approximately coincident with the directions 

 of the striae. 



If we refer to the analogous phenomena of Scotland, we find the 

 general law which characterises them is exactly that above enun- 

 ciated ; but when we examine the details of this latter case, it ap- 

 pears that the general law is only approximately true, for the law 

 of divergency does not accurately hold with reference to one gene- 

 ral centre, but with reference to a number of particular centres. 

 This I have proved in the memoir on the granitic blocks of the 

 South Highlands of Scotland, inserted in the last Number of our 

 Journal, with respect to the granitic nucleus of Ben Cruachan, and 

 that of the group of mountains immediately on the west of the 

 northern part of Ben Lomond. To complete our knowledge of the 

 Scandinavian striae, it is necessary to ascertain whether such par- 

 ticular centres are found also in the mountainous district of that 



