' •'■ xxv 



11. 





-\ 



•^utei. 



ed 



' "^^'^ still 

 P^'incipai 



e 



lave 



COll- 



'>ted by a 

 •keu of iu 



^ the sim- 



1 



■ -i then l)e 



imorgenee 

 t L'lilf and 



ancient 



• ■ 



ronisi are 



matter. 



[his sreat 



iiuiiiy ob- 



rlomerate 



tracli}-te. 

 t of that 



miaaie of 



losed 



eonil 

 of 1.887 



uaneJ by 



is i^'^-"^^f 

 is nni^l; 



liiiati*^^' 



TlS 



v^coi 



•ain? 



Ch. 



II.] 



SANTORIN. 



r-o 



to M. Bory St. Vincent, have the same direction as those of 

 the other isles of the Grecian Archipelago, namely, from 



NNW. to SSE. Each of the three islands, Thera, Therasia, 



com 



tuff, having a gentle inclination of only 3"" or 4°. Each bed is 

 very narrow and discontinuous, the successive layers being 

 moulded or dove-tailed, as M. Virlet expresses it, into the in- 

 equalities of the previously existing surface, on which showers 

 of cinders or streams of melted matter had been poured. 



An important fact is adduced by M. Yirlet, to show that 

 the gentle dip of the lava streams in the three outer islands 

 towards all points of the compass, away from the centre of 

 the gulf, has not been due to the upheaval of horizontal beds, 

 as conjectured by Yon Buch, who had never visited Santorin."^ 

 The French geologist found that the vesicles or pores of the 

 trachytic masses were lengthened out in the several directions 

 in which they would have flowed if they had descended from 

 the axis of a cone occupying the centre of the crater. For 

 it is well known that the bubbles of confined gas in a fluid in 



form 



B 



axis coincides always with that of the stream. 



The absence of dikes in the cliffs surrounding the gulf is 



in favour of the theory that we here behold a section of 

 the basal remains of an old volcanic cone. We have already 

 spoken of the want of such dikes in those parts of the old 



Somma 



Etna, which 



from 



(YoL II. p. 17.) We may 



from analog} 



that the 



part 



Kaimenis 



of steeply inclined lavas traversed by numerous vertical dikes. 

 If we adopt the hypothesis above suggested, we are re- 

 quired to assume a subsidence of 



more 



order to explain the north-east channel (B, fig. 95, and &, fig. 

 97) as being a submerged valley or ravine of subaerial erosion. 

 In reference to this point we may mention that a large part 

 of Thera actually sank down during a great earthquake in 



* Poggendorf s Annalen 1836, p. 1S3. 



