Volcanoes, 271 



volcanoes. That the eruptions are as numerous as from sub- 

 aerial craters there can be no doubt, but they are much less 

 liable to be observed. It is a singular fact, that we are ac- 

 quainted with scarcely an instance of subaqueous eruption 

 that has not produced an island, and yet it may be reasonably 

 supposed that many do occur which have not sufficient energy 

 to elevate the mineral masses above the level of the sea. 

 This circumstance may be accounted for in two ways. It is 

 probable that the volcanic vent is sometimes superposed by 

 so great a depth of water that no effect is produced on the 

 surface by the eruption ; at other times the energy which is 

 exerted is sufficient to occasion many phenomena on the 

 surface of the water ; but no observer is present, and there- 

 fore, in this instance, as well as the other, we gain no inform- 

 ation concerning the activity. 



The most remarkable subaqueous eruptions of which we 

 have any account are those which have troubled the Sea of 

 Azof, the Azores*, and the Island of Santorino in the 

 Grecian Archipelago : we shall only dwell upon the pheno- 

 mena which attended the latter. 



The Island of Santorino, in the Grecian Archipelago, was 

 formerly known by the name of Thera. Pliny, speaking of 

 it, says, " There is a tradition that it rose out of the sea ;" and 

 supposes it to have occurred in the 135th Olympiad, or 

 about 237 years b. c. 



By the agency of a subaqueous volcano in the neighbour- 

 hood of Santorino, several islands have at various times been 

 formed, and perhaps Santorino itself had its origin from the 

 same cause. 



Hiera rose from the sea in the year 197 B.C. 



Thia - ^ - - - 40 A.D. 



Thia and Hiera were united - 726 A.D. 



Little Kamenoi was formed - 1573 A.D. 



On the 22d of May, 1707, the volcano again burst into 

 action, and the islands around were violently agitated by an 

 earthquake. On the following morning a new island, Isola 

 Nuova, was discovered. A few days after, several persons 

 ventured to land, the agitation having apparently subsided ; 

 but during their stay the island began to tremble exceed- 

 ingly, and they hastily left the treacherous ground on which 

 they had trespassed. 



In July there arose, at a distance of about sixty paces 

 from the new island, a ridge of black rocks, from which 

 torrents of smoke issued. The inhabitants of Santorino were 



* See an account of the formation of the Island of Sabrina, PhiL 

 Trans., vol. cii. p. 152. 



