THE GRAND ERUPTION OF VESUVIUS IN igo6 653 



authority of the director of the Vesuvian Observatory, that this 

 truncation amounts to 250 meters, or about 800 feet; but when the 

 writer visited the observatory on the 12th, Professor Matteucci 

 stated that he had never given out this estimate. The height of the 

 cone before the eruption was not far from, though probably in excess 

 of, 4,265 feet (1,303 meters on the mihtary map of 1900), while 

 the Punta del Nasone reaches 3,779 feet. 



Truncations of the same order of magnitude have occurred in 

 1 63 1 and 1794.^ 



In place of the beautiful outlines which the cone of Vesuvius 

 presented before the recent eruption (see Figs. 4 and 5), it now shows 

 a flat dome corresponding to the larger crater and the wider radius 

 of distribution of the ejectamenta (see Fig. 13). Its somber hue 

 is replaced by the dim gray color of sand which seems to extend 

 almost to its base, where before was the rich green of a sub-tropical 

 vegetation. 



Apparent relationships 0} events. — The recent eruption of Vesu- 

 vius belongs to the paroxysmal rather than to the explosive type, 

 though no sharp line divides the two. The order of events has been 

 that generally recognized to be characteristic of this type. Starting 

 in this instance from almost absolute repose in October, 1904, activity 

 in the crater increased gradually, and lava began to dribble from 

 a bocca high up upon the inner cone late in May of the following 

 year. Both these manifestations of returning life increased more or 

 less steadily until early in April, 1906, when the grand stage was 

 ushered in. It may be presumed that during these initial stages 

 lava found its way to the bocca from which it issued through a com- 

 paratively narrow channel, since otherwise the weak inner cone, 

 especially in its upper portion, could hardly have withstood its hydro- 

 static pressure. This channel must have been slowly but constantly 

 widened through the gradual fusion of its walls, thus augmenting 

 both the quantity of lava which could reach the bocca and the hydro- 

 static pressure of the column upon the now weakened walls. When 

 the cone was no longer able to withstand the pressure, it was cleft 

 radially to the accompaniment of light earthquakes,^ with partial 



1 J. Roth, loc. cit. 



2 These earthquakes were felt in Naples, one in the late evening of the 7th, and 



