200 M. Von Buch an Vokanos and Craters of Elevation. 



ter of elevation in its centre, but without a solid nucleus. In 

 the crater of Astruni, the compact masses rise up in a dome-like 

 form ; but they are not broken up — no lasting communication 

 with the interior, in short, no volcano is produced. These masses 

 remain, as it were, a model of the great trachytic unopened 

 domes, which are so numerously scattered over the surface of 

 the globe, and of which we have examples in the Pui/ de Dome 

 and Chimborazo. Vesuvius^ finally, does not rise up alone, but 

 exhibits also the required permanent communication which we 

 see opened at its summit, and thus affords an example of a true 

 volcano. It is probable that even the spectacle, and the oppor- 

 tunity of investigating so extraordinary a series of events, will 

 in a short time be presented to us. In the beautiful and exten- 

 sive elevation-crater of Santorin, which is composed of strata of 

 tuffa, trachytic masses have been raised up as in Astruni, but 

 only in detached and but slightly-continuous rocks. The bot- 

 tom of the crater has, near the land, a depth exceeding 600 feet. 

 For a series of years this bottom has been rising gradually from 

 the middle of the crater. The depth of the sea is constantly di- 

 minishing, and at the present time, the raised up land is very 

 near the surface. We have here evidently an example of a tra- 

 chytic dome, which will probably rise much higher than the sur- 

 rounding edges of the island ; and it is quite possible, nay, ex- 

 tremely likely, when we remember the violent movements to 

 which the northern part of the Morea is exposed, that the moun- 

 tain which is now being elevated will at length break out, and 

 form a volcano. M. Virlet was the first to make known this un- 

 expected and remarkable fact,* and it is too instructive and im- 

 portant to allow us to pass it over without quoting the words of 

 the author. The island, says Virlet, is rising between Micro- 

 Kameni and the haven of Thira in Santorin. Twenty years 

 ago, it was fifteen yards under the surface of the sea; in 1830, 

 Colonel Bory and M. Virlet found that the depth was only from 

 three and a half to four yards. Since that time, the depth has 

 been so much diminished, according to the public journals, that 

 the appearance of the island may be speedily expected. Its sum- 

 mit extends 2400 feet from east to west, and 1500 feet from 



' Bulletin de la Soc. Geol. de France, iii. p. 1 09 ; and Edin. New Phil. 

 Journal, vol. xxi. p. 175. ' 



