272 



Volcanoes. 



greatly alarmed at this new phenomenon ; and so prejudicial 

 was the vapour, that many of the inhabitants were killed by 

 inhaUng it, and all, more or less, felt its effects. On the 31st 

 the sea seemed as though ready to boil, and in two places 

 near the island revolved in circular eddies. During the 

 whole of this time the volcanic agent was in a state of great 

 activity, but varied in its manner of operation. 



On the 23d of May, the phenomena assumed a less terrific 

 aspect, and from that time gradually decreased in violence ; but 

 during the following ten years the volcanic agent continued in 

 a state of partial excitement, the surrounding islands were 

 occasionally troubled with earthquakes, and the inhabitants 

 alarmed by subterranean noises. 



The following sketch [Jig. 62.) may bring to mind the rela- 

 tive positions of the island group. 



The Island of St. Mi- 

 chael's, which is the largest 

 of the Azores, is described 

 by Dr. Webster as en- 

 tirely formed of volcanic 

 rocks. It is famous for 

 the number of its hot 

 springs, which are greatly 

 impregnated with sul- 

 phuric acid, and sulphur- 

 etted hydrogen. Several 

 subaqueous eruptions oc- 

 curred in its neighbour- 

 hood between the years 

 1638 and 1720. From 

 the latter date to the year 

 1811, the volcanic agent 

 remained in a state of re- 

 pose; but during that year 

 it again burst into action, 

 and a new volcano was formed. This product of its throes stood 

 about 300 ft. above the level of the sea, and was about a mile 

 in circumference, but after a short time sunk again into its 

 watery bed. This is frequently the case with islands formed 

 by submarine action. During the time of eruption, columns 

 of smoke rise from the sea ; the waters are much agitated, and 

 rendered very impure ; scoriae and lava are ejected ; and at 

 last an island is formed, which is fated to sink into its watery 

 bed a few hours after it has been raised. 

 (^To be continued.) 



A, Santorino. B, Therasia. c, Hiera. 



D, tittle Kamenoi. e, Black Island, formed in 1707. 



