Page:Quarterly Journal of the Geological Society of London, vol. 27.djvu/428

 of belief in the theories of Werner ; and as he had found fossil-shells in one of the sandstones of the island, he went on to speculate on the probability that the basalt, which alternated with these sandstones, would eventually be found to contain fossils*. The most detailed account of Eigg which has yet appeared, is that published by Dr. Macculloch in 1819†. He pointed out the clear order of succession of the rocks shown by the cliff-sections, and noticed some of the more marked varieties, both among the stratified and the igneous series. He showed also the relation of the secondary rocks to those of Skye and the rest of the western islands, and connected the igneous masses with those of the surrounding regions. Although he visited the island at least twice, he seems to have contented himself with the examination of those portions which were easiest of access. Hence some of the most interesting features of the island escaped his notice. About twenty years later Mr. Hay Cunningham communicated to the Wernerian Society a short but interesting paper upon the geognosy of Eigg. He gave some details as to the petrography of the igneous rocks, but added nothing to our knowledge of the geology, his remarks on the origin and position of the igneous rocks being founded on a misconception of the twofold interbedded and intrusive character of these masses‡. Hugh Miller, in the course of a cruise among the "Western Islands, spent some time at Eigg. His attention was more particularly directed to the fossil-contents of the oolitic strata, of which he made a collection, and which he has to some extent described. He did not add any new facts to the known geology of the island §.

C. Oolitic Series.

Although the detailed account of the Oolitic rocks of Eigg falls to be given in a subsequent paper, some brief reference to them may be inserted here. Measured from the sea-level at Tallam to the base of the overlying sheets of basalt in the cliff at Dunan Thalasgair, the stratified rocks attain a thickness of probably not less than 600 feet ; though, owing to the way in which they are split up by intruded sheets of basalt, and concealed by landslip- rubbish, their depth cannot be precisely determined. As the general


 * Jameson's ' Mineralogy of the Scottish Isles,' vol. ii. pp. 36-47.

† Macculloch' s ' Description of the Western Islands of Scotland,' vol. i. pp. 507-522.

‡ Hay Cunningham, Mem. Werner. Soc. vol. viii., 1839. This author insists that the igneous rocks of Eigg, as well as those of Scotland generally, were erupted and consolidated beneath the surface, there being no proof, according to him, that any of the basalts ever flowed out as a stream at the surface. With regard to the Scur of Eigg, he says, " it can be confidently asserted that it exists as a great vein, which has been erupted through the older plutonic rocks " — a statement which has generally been accepted, but which, as will be shown in this paper, is wholly inadequate and incorrect.

§ See his ' Cruise of the Betsy,' p. 31 et seq. ; ' Sketch-Book of popular Geology,' p. 137. Several foreign geologists and mineralogists have noticed the rocks of Eigg. Necker de Saussure gave a detailed description of the mineralogy of the Scur (' Voyage en Ecosse,' ii. p. 449 et seq.).