Notice of Active and Extinct Volcanos. 289 



The Cape de Verd Islands are little known (geologically,) 

 but " they are said to consist principally of volcanic matter, 

 and the island of Fago contains an active volcano." 



The Azores are thoroughly volcanic. Dr. J. W. Webster, 

 of Boston, U. S. Am. has given us a very interesting account 

 of them.* Trachyte, obsidian, pumice, &c. abound there. 

 There is an ancient crater in St. Michael fifteen miles in 

 circumference, containing a lake and the rest covered with 

 vegetables and a thin population. There are great caverns 

 in the lava like those observed in Iceland by Sir George 

 Mackensie, and in them hang the congealed droppings, in 

 the form of stalactites — curious arborescent figures, &c. 



In St. Michael there are hot springs charged with carbonic 

 acid and sulphuretted hidrogen gases and a siliceous sinter 

 is deposited, similar to that of the Geysers in Iceland. That 

 volcanic energy is still active beneath the seas in this region, 

 is evident, from the remarkable occurrence of the rise of a 

 volcanic island through the ocean. 



" In the year 1811 a phenomenon occurred, similar in kind to 

 that, which I have already described, as ha zing happened in the 

 Grecian Archipelago. After a succession of earthquakes, expe- 

 rienced more or less sensibly in all the neighboring parts, a new 

 island arose in the midst of the sea, of a conical form, and with a 

 crater on its summit, from which flame and smoke continually is- 

 sued. The island, when visited soon after its appearance by the 

 crew of the frigate Sabrina, was about a mile in circumference, 

 and two or three hundred feet above the level of the ocean, it 

 continued for some weeks, and then sunk again into the sea." 



Dr. Webster has given drawings and a very interesting de- 

 scription of this remarkable occurrence so instructive in the 

 history of volcanos. 



Among the Azores, El Pico is the only one which contains 

 a volcano at present in activity ; its summit is not less than 

 nine thousand feet above the sea ; it consists of a conical 

 mass of trachyte, and is constantly emitting smoke. 



Ascension Island is of volcanic origin, containing abund- 

 ance of ignigenous materials, particularly in a hill about 

 seven hundred feet above the sea, in which is a hollow, pro- 

 bably a crater now filled with volcanic substances. The island 



* See the notice of Dr. Webster's work, Vol. IV, page 251 of this Journal. 

 Vol. XIII.— No. 2. 12 



