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Ch. XXVI.] 



BATE OF ADVANCE OF LAVA STREAM. 



23 



between 3,000 and 4,000 inhabitants, arrived at length at 



the walls of Catania. These had been purposely raised 



flood accumulated 



to protect the city; but the burning 

 till it rose to the top of the rampart, which was 60 feet in 

 height, and then it fell in a fiery cascade and overwhelmed 

 part of the city. The wall, however, was not thrown down, 

 but was discovered long afterwards, by excavations made in 

 the rock by the Prince of Biscari ; so that the traveller may 

 now see the solid lava curling over the top of the rampart as 

 if still in the very act of falling. 



This great current performed the first 13 miles of its 

 course in 20 days, or at the rate of 162 feet per hour, but 

 required 23 days for the last two miles, giving a velocity 

 of only 22 feet per hour ; and Ave learn from Dolomieu 

 that the stream moved during part of its course at the rate 

 of 1,500 feet an hour, and in others took several days to 

 cover a few yards.^ When it entered the sea it was still 

 600 yards broad, and 40 feet deep. It covered some ter- 

 ritories in the environs of Catania, which had never before 

 been visited by the lavas of Etna. While moving on, its 

 surface w^as in general a mass of solid rock ; and its mode 

 of advancing, as is usual with lava streams, was by the 



of the solid walls. A gentleman of 



to secure the city 

 from the approach of the threatening torrent, went out with 



a party of 50 men whom he had dressed in skins to pro- 

 tect them from the heat, and armed with iron crows and 

 hooks. They broke open one of the solid walls which flanked 

 the current near Belpasso, and immediately forth issued a 

 rivulet of melted matter which took the direction of Paterno ; 

 but the inhabitants of that town, being alarmed for their 

 safety, took up arms and put a stop to further operations, f 



As another illustration of the solidity of the walls of an 

 advancing lava stream, I may mention an adventure related 

 by Eecupero, who, in 1766, had ascended a small hill formed 

 of ancient volcanic matter, to behold the slow and gradual 



occasional Assuring 



Catania, named Pappalardo, desiring 



^ See Prof. J. D. Forbes, Phil. Trans., 1846, p. 155, on Velocity of Lava. 

 t Perrara, Descriz, della Etna, p. 108. 



