702 
Proceedings of the Royal Society 
the island. At least, such was the opinion I formed after a 
week’s ramble, and after inquiring among intelligent persons well 
acquainted with the rocks of the island. 
So also in the Island of Kerrera, opposite to Oban, there are 
numerous blocks of grey granite, though no rocks of any kind of 
granite occur in the island. 
On the small island of Staffa, consisting entirely of basalt and 
greenstone, I found boulders of red granite and gneiss, which 
probably came from the Mull mountains, situated to the N.E. 
(Committee’s 2d Rep., p. 157). 
(2.) In Nairnshire there are many conglomerate boulders of huge 
size, and angular in form, which must have been transported across 
what is now the Cromarty Firth from Ross-shire. They are at a 
height of from 400 to 600 feet above the sea. (First Rep. of Com- 
mittee, p. 42.) 
Other examples are afforded by the black granite boulders at 
Appin and in Loch Creran. Specimens of these are now on the 
table. As the present Report gives a full explanation regarding 
these boulders, I do not require to repeat how, when these speci- 
mens were submitted to Professor Judd of London, who has made 
the igneous rocks of the West Highlands a special study, he 
gave his opinion that there was no rock of the same description on 
the mainland, and that it was to be found only in Mull. From 
that island, therefore, these boulders must have been transported, and 
across a sea, which even now has at one place a depth of 100 
fathoms, but which transportation probably took place at a period 
when the sea stood hundreds or even thousands of feet above 
its present level, or when the land sat that much lower in the 
ocean. 
(3.) If Professor Judd’s opinion of the Loch Creran and Appin 
boulders be correct, it goes far beyond an explanation of the boulders 
in these localities. For example, the Island of Lismore, whose rocks 
are entirely limestone, has on it many boulders of granite, which 
probably also came from Mull, inasmuch as Lismore lies between 
Mull and Appin (Com. 2d Rep., p. 157). In Lochaber, there is the 
hill called Craig Dhu, about 2000 feet in heig'ht, so called, I believe, 
from the great number of black granite boulders resting on and near 
its top. These boulders, on account of their peculiar colour as well 
