114 GEOLOGY OF ARRAN. 



tion under the shelter, sunshine and moisture has covered 

 the floors with a deep deposit, in which it is hopeless 

 to search. We have added nothing to the list originally 

 given by Mr Ramsay, and which comprises the following: 



Cardium laevigatum. Venerirupis decussata. 



Patella vulgaris. palaestra. 



Lucina radula. Mytilus edulis. 



Purpura lapillus. Buccinum undatum. 



Turbo littoreus. Venus fasciata. 



Turbo rudis. Cytherea exoleta. 



Trochus cinerariue. Terebra reticulata. 



magus. Rissoa calathisca. 



crassus. seuricostata. 



Nerita littoralis. 



Three of these the Venerirupis decussata, Rissoa calathisca, 

 and Trochus crassus are now rare in the West of Scotland. 

 These species therefore seem to connect the beds in question 

 with those containing species now extinct in the seas around 

 Britain. The young geologist needs to be cautioned about 

 drawing any conclusion from a few scattered shells found on 

 the hills, as birds often carry shells even of considerable size 

 up among the mountains. It is only a regularly formed bed 

 that affords evidence of physical changes in the surface. 



58. As we approach the village of Corrie, the sea cliff 

 becomes lower, and on the edge of it there rest two huge 

 granite boulders, one on each side the White Water, which 

 here comes tumbling down from the corrie on the north-east 

 side of Goatfell. They are true boulders, granite resting on 

 sandstone. The larger of the two, and the largest boulder 

 in the island, lies on the north side of the stream. We 

 estimate the weight at more than 2000 tons ! What force 

 could have hurled a mass so enormous from the mountain- 

 side? Not gravity urging its descent; unless, perhaps, the 

 first impulse was given by an earthquake, for the slope of 

 the hill-side is gradual, and the mass itself ill adapted for 



