64 SECRETS OF EARTH AND SEA 



During the nineteenth century it was a permanent feature 

 of the mountain, though a good deal cut down in 1822, 

 and later grew so high as to give a total elevation from the 

 sea-level of 4300 ft. The crater at the top of the ash-cone 

 has varied during the past century in width and depth, 

 according to its building up or blowing away by the central 

 steam jet. In 1822 it is reported to have been funnel-like 

 and 2000 ft. deep, tapering downwards to the narrow 

 fissures which are the actual vent. At other times it has 

 been largely filled by debris, and only 200 ft. deep. 

 Molten lava has often issued from fissures in the sides of 

 the ash-cone, and even lower down on the sides of the 

 mountain, and a very small secondary crater has some- 

 times appeared on the side of the ash-cone 100 ft. or 

 200 ft. from the terminal crater which "finishes off" 

 the cone. 



Such was the condition of the mountain when I first 

 saw it in the autumn of 1871. Six months later I witnessed 

 the most violent eruption of the nineteenth century. 

 Vesuvius kept up a continuous roar like that of a railway 

 engine letting off steam when at rest in. a covered station 

 only a thousandfold bigger. Its vibrations shook with a 

 deep musical note, for twenty-four hours, the house nine 

 miles distant in Naples in which I was 'staying. My 

 windows commanded a view of the mountain, and when 

 the noise ceased and the huge steam-cloud cleared away, 

 I saw a different Vesuvius, the higher part of the ash-cone 

 was gone, and a huge gap in it had been formed by the 

 blowing away of its northern side. 



In October 1871, when I joined my friend Anton 

 Dohrn at Naples in order to study the marine creatures 

 of the beautiful bay, Vesuvius was in the proud possession 

 of a splendid cone, completing its graceful outline. A 

 little steam-cloud hung about one side of the cone during 

 the day, and as night came on Vesuvius used, as we said, 



