VOLCANIC PHENOMENA. 103 



or sulphurous, and loaded with mud, are the most simple transi- 

 tory results. But frequently there are, also, through the upheaved 

 and broken ground, amidst violent detonations, explosions which 

 eject, to a great distance, all the debris of the formation, as 

 happened at Saint-Michel, in the Azores, in 1522, where the 

 debris of two hills covered the whole city of Villa-Franca. It 

 most frequently happens, at the same time, that more or less con 

 siderable eruptions of incandescent matters take place, consisting 

 of scoriae, pumice, &c., in a mefted state, which are either projected 

 to a distance, or run on the slopes, or accumulate on the spot to a 

 greater or less height ; this has occurred in a great many localities. 



Eruption of the island of Saint George. In the month of May 1808, in 

 the island of Suint George, one of the Azores, the soil in the midst of culti- 

 vated fields after being upheaved opened at many points with a fearful noise. 

 It first formed a vast cavity, or crater, of 100,000 square yards, then a 

 smaller one at the distance of a league, and finally twelve or fifteen little 

 craters on the broken surface. An enormous quantity of scoriae and pumice 

 was projected to a distance, and the ground was covered a yard and a half 

 deep over an extent a league wide and four leagues long. For more than 

 three weeks afterwards currents of melted matter flowed from the principal 

 crater to the sea. 



Monte. Nuovo. Monte-Nuovo, formed in 1S38, at the bottom of the bay 

 of Baia, on the coast of Naples, is another example of a similar eruption. 

 Violent earthquakes had continued during two years : on the 21th and 28th 

 September they did not cease either day or night ; the plain found between 

 Lake Averne, Monte- Barbara and the sea, was then upheaved, and various 

 cracks were evident, fyc. (Pietro Giacomo di Toledo). Then a great extent 

 of ground was elevated, and suddenly assumed the form of a growing moun- 

 tain ; in the night of the same, day this little mountain of earth opened with 

 a great noise, and vomited flames, as well as pumice, stones and cinders 

 (Porzio). The pumice came from the upheaval of the soil, which consists 

 of this material throughout Campa/nia ; and the stones and cinders came 

 from the eruption which occurred at the moment : we still see on the south 

 side of the mountain a ridge of scoriae, and on its summit the crater which 

 produced them. The eruption lasted seven days, and the matters projected 

 and ejected partly filled Lake Lucrin. From that time the most perfect 

 tranquillity has prevailed. 



Jorullo. There was something analogous, but under peculiar circum- 

 stances, in what happened in Mechoacan, noar the town of Ario, on the 

 29th September, 1759, after an earthquake of two months duration. In the 

 midst, of a plain covered with sugar-cane and indigo, and traversed by twc 

 rivulets, there formed in a single night, says M. Humboldt, a gibbosity 

 (bunching up) 1 BO yards high near the centre, covered by thousands of 

 small smoking cones, in the midst of which were raised up six great hil- 

 locks, arranged in one line (Jig. 184), in the direction of the volcanoes of 

 Colima and of Popocatapctl. The highest of these hillocks, called Jorullo, 

 was more than five hundred yards in height above the plain ; from its sides 

 escaped a great quantity of lavas. 



Vesuvius. Something similar must have occurred in Vesuvius, for Strabo 

 describes the mountain so called by the ancients without in any way allud 

 ing to the remarkable cone which now exists ( fig. 185), and which he 

 would not have failed to mention. It is evident this cone did not then 

 exist; but the crests which rise in semicircles on the north, forming what 

 is new called the somma, probably constituted part of a ooniplete circle; the 



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