638 WILLIAM HERBERT HOBBS 



The greatest of the subsequent eruptions have occurred in 1737, 

 1794, and 1822; in all of which outbursts the cone suffered con- 

 siderable reductions in altitude. In 1855 also it is said to have lost 

 almost 60 meters. In the eruption of 1737 Portici, Resina, and 

 Torre del Greco were all again invaded by lava, as was the latter 

 city in 1794. Of the eruptions which have taken place in 1822, 

 1839, 1850, 1855, 1861, 1872, 1899, and 1903, much the most important 

 have been those of 1822 and 1872. The last mentioned was of 

 considerable interest because of its rapid development, and because 

 of the favorable conditions which it offered for observing and photo- 

 graphing the mountain. Great quantities of steam were given off; 

 and the lava, which flowed in the direction of San Sebastiano, was 

 typical of the "ropy" surface sometimes assumed by volcanic mag- 

 mas. In recent years small quantities of lava have for quite long 

 periods oozed from elevated hocche. 



No volcano has received the same amount of study as Vesuvius, 

 and the greatest amount of accurate knowledge of it has been brought 

 together upon the map of Dr. Johnston-Lavis.^ 



Chronicle of events during the eruption of 1906. — During late 

 September and early October, 1904, Vesuvius was in almost absolute 

 repose. The eruption of lava began May 27, 1905. The charts 

 kept at the Osservatorio Vesuviano to indicate the grade of activity 

 show absolutely no change at the time of the great Calabrian earth- 

 quake of 1905 (September 8), the curve of activity for days before 

 and after that disturbance being almost horizontal. In October and 

 November, 1905, lava was dribbling from an outlet high up upon 

 the central cone and near the funicular railway. At night it showed 

 from Naples as a bright red line, which later forked near the Atrio 

 del Cavallo. This stage with the gradual augmentation of activity 

 continued until the first days of April, 1906. 



On the 5th of April there was a very decided increase in the vio- 

 lence of the explosions, and an ash cloud mounted high above the 

 crater (see Fig. 6). The climax was reached on the evening of the 

 7th (Fig. 7), when three earthquakes were felt in Naples of sufficient 



I Geological map of Monte Somma and Vesuvius constructed by H. J. Johnston- 

 Lavis during the years 1880-88. Scale 1:10,000 (6.33 inches to the mile). In 

 six sheets. 



