320 RAMBLES OF A GEOLOGIST. 



eight hundred feet over it ; and yet both hills to their sum- 

 mits are mottled over with granite boulders, furnished by the 

 comparatively low-lying boss. One of these travelled masses, 

 fully two t6ns in weight, lies not sixty feet from the summit 

 .of the loftier hill, at an altitude of nearly fifteen hundred feet 

 over the sea. Now, it seems extremely difficult to conceive 

 of any other agency than that of a rising sea or of a subsid- 

 ing land, through which these masses could have been rolled 

 up the steep slopes of the hills. Had the boulder period 

 been a period of elevation, or merely a stationary period, dur- 

 ing which the land neither rose nor sank, the travelled boul- 

 ders would not now be found resting at higher levels than 

 that of the parent rock whence they were derived. We oc- 

 casionally meet on our shores, after violent storms from the 

 sea, stones that have been rolled from their place at low ebb 

 to nearly the line of flood ; but we always find that it was 

 by the waves of the rising, not of the falling tide, that their 

 transport was effected. For whatever removals of the kind 

 take place during an ebbing sea are invariably in an opposite 

 direction ; they are removals, not from lower to higher 

 levels, but from higher to lower. 



The upper subsoils of Scotland bear frequent mark of the 

 elevatory period which succeeded this period of depression. 

 The boulder-clay has its numerous intercalated arenaceous 

 and gravelly beds, which belong evidently to its own era ; 

 but the numerous surface-beds of stratified sand and gravel 

 by which in so many localities it is overlaid belong evident- 

 ly to a later time. "When, after possibly a long protracted 

 period, the land again began to rise, or the sea to fall, the 

 superior portions of the boulder-clay must have been exposed 

 to the action of tides and waves ; and the same process of 

 separation of parts must have taken place on a large scale, 

 which one occasionally sees taking place in the present time 

 on a comparatively small one, in ravines of the same clay 



