Personal Yisits to Mount Vesuvius. 123 



as a low rim occasionally overtopped by tlie flows of lava from 

 above. This modern cone bas, by these eruptions, been not only 

 by degrees greatly enlarged and heightened, but also repeatedly 

 emptied by paroxysmal explosions, and again filled by minor 

 eruptions of lava and fragmentary matter from the bottom of the 

 crater so formed. The last of these great crater -forming paroxysmal 

 eruptions occurred in 1822, by which some six hundred feet of the 

 top of the mountain were blown off. Since which time not only has 

 the great crater then formed — nearly three miles in circumference, 

 and upwards of 1,000 feet deep — been re-filled and re-emptied more 

 than once, but a new and solid cone has been raised above to a 

 greater height than the mountain had before 1822. These changes 

 are well exemplified in the woodcuts given in this volume, and it is 

 evident, that, from the accumulation of the fragmentary matter and 

 lavas so continually emitted, the mountain is rapidly growing in 

 external bulk ; so that, if the process continues, we may anticipate, 

 with the Professor, a time when the valley called the Atrio, which 

 now separates the cone of Vesuvius from the half- encircling ridge of 

 Somma, will be obliterated, and the whole form but a single conical 

 mountain of as great height and bulk as it probably had some 3,000 

 years ago. If it be asked, what has become of the matter ejected 

 from the central hollows so repeatedly blown out and re-filled 

 within the heart of the mountain ? The answer is, it has been 

 spread by the winds in showers of ashes over the surrounding lands 

 and seas to the distance sometimes of hundreds of miles. The lavas 

 do not always proceed from the summit of the cone, but often well 

 out at lower levels from radial fissures broken through its sides, and 

 these streams consolidate into buttresses, which, together with the 

 heavier ejected fragments that fall from the air, add continually to 

 the bulk and strength of the entire mass. One of the latest and 

 most remarkable phenomena was the elevation to the amount of 

 three and a-half feet of the sea coast at the foot of the mountain in 

 front of Torre del Greco, behind -which town, and at no gi'eat 

 distance, one of these lateral eruptions was at the moment taking 

 place from no less than ten openings in a line from the axis of the 

 cone. 



The author adds to his history and description of Vesuvius a 

 similar, but briefer, account of the adjoining Campi Phlegrfei, and 

 justly refers the production of the numerous craters of this district, 

 with their encircling hills of tufa, to submarine eruptions on a 

 shallow shore. To the same process he ascribes the much contested 

 origin of the Monte Nuovo, the latest formed of these cones and 

 craters. For, we need hardly say, the Professor is no partisan of 

 the untenable doctrine of " upheaval craters," which has so confused 

 the ideas of many Geologists on the phenomena of volcanoes. Sub- 

 marine tuffs, more or less stratified, and dating probably from the 

 period when these Phlegrean vents were in greatest activity, form 

 the substratum of Somma itself, as well as of nearly all the Campania 

 around, and have been raised to their present position, together with 

 the general line of coast, by those subterranean movements of which 



