ON VOLCANOES AND EARTHQUAKES. 355 



he origin, it appears, of the lakes of Averno and 

 Agnano. That the ground is cavernous beneath the 

 craters of volcanoes, is proved by their sound, and 

 by the vapours which they emit ; appearances re- 

 markable at Vulcano and in the Solfatara ; the latter 

 being a tract which has maintained its character un- 

 varied since a period anterior to Roman history, 

 giving rise to some of the well-known mythological 

 fables of the antients. 



In Europe and in Asia, those volcanoes which are 

 well known, appear to be detached, whatever un- 

 known communications they may possess beneath ; 

 but in America, they are sometimes arranged in rows, 

 as in Chili and Guatimala. Antisan and Pichinca in 

 Peru, are prolonged ridges. This fact has given rise 

 to some speculations on the seat of the fire, which 

 will come under review hereafter. 



The peculiar position of marine volcanoes renders 

 it necessary to record a few of the appearances which 

 they present. In 1707, near St. Erini in the Greek 

 Archipelago, a volcanic island was formed, which, in 

 less than a year, attained a circumference of five miles, 

 with an altitude of forty feet. A similar one of 

 smaller dimensions was also produced in the same 

 place. In the same manner, islands have been gene- 

 rated near Iceland and the Azores, at different periods ; 

 and it is not long since a small spot was thrown up 

 among the latter ; shortly after washed away, from 

 having been formed of loose materials. In the Pa- 

 cific ocean, these events have frequently happened; 

 and though the islands thus produced are sometimes 

 low, they occasionally attain a considerable altitude, 

 as is the case with Ascension. But I may refer to 

 the accurate work of Von Hoff for numerous details 

 on this subject. 



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