Page:Transactions of the Geological Society, 1st series, vol. 3.djvu/71

 characters of the southern part of the group, Garsven and Blaven, since I was unable to procure access to the other portions of it.

In other parts of Sky we have seen that the greenstones as well as the other varieties of trap, are disposed in a flat or apparently stratified manner by which the general aspect and outline of all these portions of the island are determined. Here on the contrary the external outline and general features are those of granite, and I may say that to its forms they appear also to add its permanence and durability. They are disposed in huge curved beds of which the external angles are, like those of granite in similar cases, slightly rounded, and they extend over considerable spaces, offering smooth sheets of rock unmarked by a single fissure or indication of past or future fractures. No eye could distinguish them from granite except by examining their composition. Their resemblance to this rock in disposition, and their dissimilarity to the greenstones of the stratified parts of the island, are in every way so decided that no position can be assumed, nor any view taken of them, however general, or on a scale however comprehensive, which can convey the slightest idea of a tendency to stratification. Nor do they in any case that I have seen shew the tendency to vertical fracture so common among green, stones, being in every respect, except that of mineral structure, entirely different from the ordinary varieties of this substance. Their granitic aspect is still further expressed in a most striking manner by the spiry forms of the summits, by their hard serrated outline and their overhanging masses, a disposition by which they are rendered inaccessible even to the stags and the wild goats that roam over this region of solitude and rocks. To this is owing their highly picturesque aspect, which bears a striking resemblance to that of the granite hills of Arran, or the more stupendous masses of the granitic