M. Von Buch on Volcanos and Craters of Elevatmi, 101 



when even a stream of lava flows from the great crater, which 

 very rarely happens, it can produce very little effect either as 

 to the increase or the external form of the mass. Even at 

 the bottom of the Val di Bove, which is a great subsidence on 

 the declivity of the volcano, the inclination of the streams is 

 still 8° or 9°f and hence their thickness is so inconsiderable 

 that their course is recognised by their black colour, and not by 

 their bank-like continuation. The form also of Etna is quite 

 regular, rising up on all sides with a uniformly advancing out- 

 line. The many, almost innumerable cones of eruption of the 

 declivity and round the base, stand like warts on the vast 

 colossus ; and the streams which flow from it so completely dis- 

 appear at a short distance, that we must necessarily regard it as 

 an absurdity to ascribe to them even the slightest influence in 

 altering the form of the mountain. 



A few of Beaumont's determinations may shew the truth of 

 the conclusion drawn : The great stream of lava which in 1669 

 destroyed many villages, and flowed past the walls of Catania to 

 the sea, burst forth at the foot of the Monti Rossi, with an in- 

 clination of 2° 58', and so proceeded eastwards from Monte Pilieri. 

 There, where the road from Nicolosi to Torre di Grifo crosses 

 this stream, its medium inclination up towards its source is 3° 45', 

 and down towards the sea 2° S^'. Near Catania, where the 

 breadth of the stream is much less considerable, its inclination 

 is 5" or 6°, but soon diminishes towards the sea. The medium 

 inclination of this rapid stream is therefore only from 2° to 3°. 

 The lower part of the stream of lava which in 1832 threatened 

 Bronte, has an inclination of 1° 51', and still presents to the eye 

 a very distinct slope. The slightly elevated streams which de- 

 scend very rapidly from the woods at Zafl*arana have a medium 

 inclination of 6° 23'. From the base towards Aci Reale where 

 they form high banks, their inclination is 2° 13'. The highly 

 inclined and broken up streams of lava between Randazza and 

 Lingua grossa vary from 4° to 4^°. 



A stream which descends from the Piano ArenosOy under the 

 summit of Etna, to the steep Val di Bove, has an inclination of 

 24°, but then it has only marked its course by a narrow line of 

 very loosely cohering slag, like all other streams which descend 

 from a similar height, with so great an inclination. 



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