PREFA TOR Y NOTE. xv 



sea-bed, as well as on land, and that sometimes new islands 

 are erupted, and sometimes submarine peaks. Thus islands 

 like Ascension, St. Paul, Amsterdam, and Reunion were, it 

 is evident from their petrological texture, formed in this way, 

 and, indeed, in one of them — Reunion — there are still two 

 volcanic vents which from time to time throw out molten rock 

 and cinders. 1 Etna and Vesuvius, it is also believed, originated 

 as submarine volcanoes on a sea-bed which was afterwards 

 elevated ; 2 and in the case of the Islands of Santorin and 

 Thracia, their structure consists of trass, scoriae, and lava- 

 sheets overlying marbles and schists. Indeed these two 

 islands form the rim of a vast volcanic crater which descends 

 for 1,278 feet below the level of the sea. They are the ' outward 

 and visible signs' of an immense submarine volcanic peak 

 which, geologically speaking, has been elevated during later 

 times, since, on them, Von Fritsch has found in several places, 

 up to an altitude of nearly 600 feet above the sea-level, marine 

 shells belonging to species which are now living in the sur- 

 rounding ocean. Fouque, who has studied these islands more 

 closely than any other observer, has arrived at the conclusion 

 that ' the volcano formed at one time a large island with 

 wooded slopes, and a somewhat civilised human population, 

 cultivating a fertile valley in the south-western district, and that 

 in prehistoric times the tremendous explosion occurred whereby 

 the centre of the island was blown out.' 3 Many more examples 

 may be found in our geological text-books. 4 



It is on such platforms as these that Dr. Murray would have 



1 Drasche in Bericht der K. K. Geol. Reichsanstadt, 1875- 1876; 

 also Velain, Les Volcans, 1884. 



2 Sartorius von Waltershausen and A. von Lasaulx, Der Aetna, 4to. 

 Leipzig, 1880, vol. ii. p. 327. 



3 Compare on the subject: Fritsch, Z. Deutsch. Geol. Ges., xxiii., 

 1 87 1, pp. 125-213 ; Fouque s Santorin et ses Eruptions, Paris 5 1880; 

 Geikie, Text- Book of Geology, London, 1885, p. 235. 



4 Such as Jukes-Browne's Physical Geology, Prestwich's Manual 

 of Geology, Geikie's Text-Book of Geology, and Philips' Manual of 

 Geology. 



