124 Geological Notes from Arran. [Sess. 



mass, in which are scattered fairly large crystals of felspar and 

 quartz. It is much weathered, and a good specimen can only 

 be obtained by a considerable expenditure of labour with chisel 

 and hammer. At Drumadoon Point there are high columnar 

 cliffs composed of this same rock, and it has a peculiar appear- 

 ance, owing to the decomposing action of the weather. The 

 whole columnar front of the cliffs — and the columns are very 

 marked — is covered with a growth of moss and lichens, and 

 reminds one of an old moss-grown ruin more than anything 

 else. Most igneous rocks exposed in this way generally pre- 

 sent a bare barren aspect, such as basalt and the dolerites of 

 Salisbury Crags, for instance. The base of the cliff is strewn 

 with huge fragments of fallen columns, and when examined 

 at a new fracture they appear to be weathered to the very 

 core. 



Of igneous rocks occurring among the Carboniferous strata 

 in Arran, cpiartz felsite is much the commonest. 



Referring once more to the pitch stones, — in Monamore 

 Glen, near Lamlash, there are in the bed of the stream, 

 near the entrance of the glen, two large beds of this rock. 

 In one of these beds two kinds of pitchstone are found — the 

 ordinary glassy variety, and a variety called spherulitic pitch- 

 stone. The latter kind is found in the middle of the vein, and 

 the spherulitic structure is due to the fact that this part of the 

 vein was cooled from the molten condition more slowly than 

 the outside portions, thus giving time for incipient crystallisa- 

 tion to take place. I obtained a specimen of pitchstone taken 

 from this spot, and also a piece of slowly - cooled ordinary 

 bottle-glass, which also shows numerous spherulites scattered 

 through its mass. 



In concluding these brief notes I will just call attention 

 to the beautiful mottled or poikilitic red sandstones, which 

 are very abundant near the place called Fallen Eocks. The 

 Fallen Eocks are about two miles from Sannox. They are 

 an immense ruin of Old Eed Sandstone blocks, which has 

 been formed by the collapse of a high far-up cliff. I believe 

 the slip happened some eighty years ago, and that the noise 

 of the fall was heard on the mainland. They form a magnifi- 

 cent spectacle, and are well worth a visit on that account 

 alone. The mottled red sandstones are to be seen on the 



