MR DAVID MILNE HOME ON THE BOULDER-CLAY OF EUROPE. 669 



defended the entire north of Europe from the shock, but probably furnished by 

 their abrasion the materials, of which the low grounds of the Continent of Europe 

 are mainly composed. In this general disposition of the mountains of Norway, 

 we see a strong analogy to the west coasts of our own islands. It appears 

 almost certain, that a common cause has devastated the western shores of nearly 

 every continent P 



It is very evident what this " common cause' 1 ' 1 alluded to by Principal Forbes, 

 as having left its mark on the western shores of North- Western Europe, must 

 have been nothing less than the ocean itself. Sir James Hall was, on the 

 limited body of facts known in his day, led to the opinion that a resistless rush of 

 waters over the country from the westward would explain the phenomena ; and, 

 down to a very recent period, attempts have been made to show how boulders 

 could be carried by what are called waves of translation. These views have now 

 been generally abandoned ; and in place of them, it has been suggested that 

 oceanic currents, with floating ice, and flowing over the submerged land, would 

 afford a better explanation — an explanation strongly supported by the great 

 extent of area over which the transporting agent has moved. 



But in stating that the agent has moved over this large extent of area in the 

 same direction, let me repeat that there are cases where the direction of the 

 striae and the transport of boulders point to a different quarter than the north- 

 west. The percentage of these cases is so small, as not to affect the argument 

 based on the generality of that direction, and on the extent of area over which it 

 prevails. 



Moreover, whilst some of these exceptional markings are undoubtedly 

 indicative of local glaciers, — the probable epoch of which will be afterwards 

 referred to, — others are not inconsistent with, but, on the contrary, are corro- 

 borative of the theory of oceanic currents. Thus, in the great glen of Scotland, the 

 lines of striae and the course of the transported boulders show a movement from 

 S.W.* So also in the estuary of the Forth, as well as in the trough which crosses 

 Scotland along the south slopes of the Kilsyth and Campsie hills, the striae and 

 many of the boulders indicate a movement from W. by S. and W. by N. Now, in 

 each of these cases, the deviation from the general or normal N.W. direction 

 coincides with the range of the valley where it occurs ; and it is not unreasonable 

 to suppose that the obstruction, caused by adjoining hills of considerable height 

 and extent, would modify the direction of the current so that it should flow with 

 some approach to parallelism with them. 



Sir James Hall, in his paper, brings out this point very clearly, when he 

 says " that the direction in the neighbourhood of Edinburgh may have been 

 occasioned by the local influence of the estuary, since the direction of the stream 



* Lond. Geolog. Society's Proceedings for April 1849, p. 13. 



