and on Boulders transported by Floating Ice 355 



scored ; but on one close to the bridge over the river Ogwyn, 

 I remarked some singular zigzag scores. At this spot the 

 cleavage of the slate is highly inclined, and owing apparently 

 to the different degrees of hardness of the laminse, smooth 

 and gentle furrows have been produced by the grinding of 

 the ice, transversely to the scores, and to the probable course 

 of the glacier. Here, as well as in some few other places, I 

 noticed an appearance which made it vividly clear that these 

 bosses had been formed by some process quite different from 

 ordinary or aqueous erosion ; it is the abrupt projection from 

 the smooth surface of a boss of a piece of rock a few yards 

 square, and one or two feet in height, with its surface 

 smoothed and scored like the boss on which it stands, but 

 with its sides jagged ; if a statuary were to cut a smidl figure 

 out of a larger one, the abrupt projecting portions, before he 

 quite completed his work, might be compared to these masses 

 of rock ; how it comes that the glacier, in grinding down a 

 boss to a smaller size, should ever leave a small portion appa- 

 rently untouched, I do not understand. 



On the summit of some of the bosses on this barrier there 

 are perched boulders ; but this phenomenon is seen far more 

 strikingly close to Capel Curig, where almost every dome of 

 rock south of the Inn is surmounted by one or more large an- 

 gular masses of foreign rock. The contrast between the rude 

 form of these blocks, and the smooth mammillated domes on 

 which they rest, struck me as one of the most remarkable 

 effects produced by the passage of the glaciers. On the sides 

 of the mountains above Capel Curig, I observed some boulders 

 left sticking on very narrow shelves of rocks, and other boul- 

 ders of vast size scattered in groups. The largest boulder I 

 noticed there was about twenty-six feet in length, by twelve 

 in breadth, and buried to an unknown thickness. 



Proceeding down the great straight valley of Nant-Fran- 

 con, which must formerly have conveyed the united glaciers 

 from Lakes Idwell and Ogwyn, we continue to meet with 

 boss-formed rocks till below the village of Bethesda. 



From this point towards Bangor, these boss-formed rocks 

 become rare : at least it is certain that a large number of 

 hummocks of rock with rugged surfaces project, whereas 

 higher up in this valley, and in all the great central valleys 



