No. I. — Account of Mount Vesuvius. 197 



tends from nearly the highest summit of the mountain to 

 where the cone merges into the Atrio del Cavalio, a well mark- 

 ed point, and the slope is very uniform. On the southern side 

 again, the slope begins more abruptly, and may be estimated 

 at the uppermost part above 46°, — a steeper slope than Hum- 

 boldt admits in any case ; nor would I for a moment wish to 

 place the result of such an imperfect estimate against the pe- 

 netration and experience of that great traveller. It only con- 

 tinues steep for a short distance, and then sweeps gently down 

 to the sea-shore, a distance of four Italian miles. See the sec- 

 tion in Plate III. 



Having now discussed as far as I can at present attempt the 

 general external features of the volcano, let us take a short sur- 

 vey of some other geological features and the peculiarities of 

 one or two important localities of the mountain Had I thought 

 myself equal to the task, I should have been glad to have en- 

 tered more minutely here into the topography of Vesuvius, and 

 given a map illustrative of the changes it has produced by its 

 phenomena, especially streams of lava during authentic record ; 

 but as the subject is so vast that I could throw little light upon 

 it, although I have been at the summit of the volcano three 

 times and inspected various portions, and as I propose in future 

 papers to discuss the phenomena of the buried cities, the for- 

 mation of tufas, and some analogous subjects, I shall confine 

 my remarks at present within narrower bounds. 



From what has already been said, it is obvious that the vol- 

 canic agency is liable to change its place and manner of acting, 

 and that it has occurred to such a degree as to change the point 

 of ejection from the Monte Somma to the modern cone. We 

 have now to observe the methods of eruption, which often 

 change from year to year. It is a mistake to imagine that lava 

 always flows from the crater of a burning mountain ; it is only 

 in particular circumstances that it can do so. The lava of 1760 

 flowed from four small craters still existing at the base of the 

 cone on the south side. One of the hillocks raised on this oc- 

 casion is 238 Neapolitan palms, about 200 feet high. In a 

 similar manner the stream of 1822 was ejected on the opposite 

 side of the mountain, and flooded the Atrio del Cavalio with 

 its fiery torrent, which was of vast extent, laying waste many 



