GLACIAL ACTION. 39 



above the river beds. Some way up the latter, also, there 

 are remarkable mounds, in a situation where, from a great 

 bend in the glen, we should expect a moraine to be thrown 

 down. Many geologists may, however, favour the idea that 

 the mounds and terraces in question were formed when cur- 

 rents swept these glens, during the gradual elevation of the 

 land. That such elevation may have been a long-continued 

 process we have already seen reason to suppose (Art. 13, 14); 

 and the effect must have been a general disturbance in the 

 sea-bed, which, joined to the action of tides produced then 

 as now, could not fail to give rise to currents of considerable 

 force. Where these met the sea, towards the mouths of the 

 glens, banks and terraces may have been thrown up; or a 

 sudden elevation of the land of a cataclysmal character may 

 have given origin to long-continued currents of sufficient force 

 to transport large blocks, and to throw down a promiscuous 

 deposit, such as we find in the mounds and terraces of the 

 mountain glens. Such sudden elevations of a range or group 

 of mountains are still regarded by many geologists as the true 

 explanation of the " diluvial phenomena ; " and it was such 

 probably that Dr. MacCulloch had in view when he spoke, in 

 the passage above quoted, " of other causes of a transient and 

 probably of a diluvian nature," as giving origin to the remark- 

 able accumulations at the mouths of the Catacol and lorsa. 



19. The dispersed blocks present phenomena still more 

 curious and of much more difficult explanation. They are 

 almost exclusively granite, a very few only of slate being 

 found. They are scattered in great numbers over every part 

 of the island, and are often of enormous magnitude. They 

 are most abundant and largest in the vicinity of the granite 

 nucleus, as about Corrie and the shore at Corriegills; and 

 generally less numei-ous, and of smaller bulk, in the remote 

 southern districts. Occasionally, however, some very large 

 ones occur even there. They are limited to no particular 

 locality, but occur alike in the valleys, on the summits and 

 northern and southern slopes of the hills, in situations to 



