288 PKOCEEDIXGS OF THE GEOLOGICAL SOCIETT. f^pr. 5, 



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 f. 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 com- 

 municated to the "Wernerian Society a short but interesting paper 

 upon the geognosy of Eigg. He gave some details as to the petro- 

 graphy of the igneous rocks, but added nothing to oxir 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 J. 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 Sekies, 



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. 



t Macculloch's ' Description of the Western Islands of Scotland,' vol. i. pp. 

 507-522. 



X 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 Geo- 

 logy,' p. 137. Several foreign geologists and mineralogists have noticed the 

 rocks of Eigg. Necker de Saussure gave a detailed description of the miner- 

 alogy of the Sciir (' Voyage en Ecosse,' ii. p. 449 et seq.). 



