19^ M. VoH Buch on Volcanos and Craters qf Elevation, 



The same is the case on Vesuvius. The broad stream of lava 

 which is crossed before the Hermit'*s Hill is reached, descends 

 with an inclination of 3°. The streams of 1804 and 1822, which 

 pass the hill of Camaldoli, from the Torre del Annunziata, have 

 an angle of not quite 4°. The last cone of Vesuvius, on the 

 contrary, rises with an inclination of 28° to 30°. Very frequent- 

 ly, much more so than in other volcanos, streams flow down this 

 steep declivity. We look out for them, in order to ascend on 

 their surface to the summit. But we never see them of great 

 extent ; they hardly ever have a greater thickness than four feet, 

 and at the edge of the crater their mass is like a ray on the 

 slope. They pierce for themselves rapidly a deep and narrow 

 furrow in the loose materials, and cannot extend at all in breadth. 

 On the 12th August 1805, Humboldt, Gay-Lussac, and my- 

 self witnessed this phenomenon. We were standing at 9 o'clock 

 in the evening on the balcony of a window in sight of Vesuvius. 

 Suddenly a line of fire shot like lightning from the summit to 

 the base, and remained fixed on the mountain like a burning 

 thread. We proceeded rapidly in a boat to Torre del Greco ; 

 but the stream had already obstructed the great road. After 

 such a sight, and after the experiments mentioned, we require 

 no further arguments to convince us that mantle-shaped masses, 

 or masses spreading out over a considerable space, cannot be 

 streams of lava which have flowed on steep declivities ; and the 

 observations of M. Elie de Beaumont give certainty to this 

 conclusion. 



Even though the beds of which Vesuvius, Somma, Etna, and 

 Stromboli are composed, were sent from the interior of the earth 

 in a liquid state, yet they cannot have been originally formed in 

 the condition in which we now find them, viz. as the surround- 

 ing masses of a steep cone ; but must have acquired their present 

 form from a cause acting on themselves, viz. the elevation round 

 an axis, which axis was opened up in the form of a crater after 

 the elevation. 



It is indeed very remarkable and striking, that this was not 

 observed at the first glance of the Vesuvius of our day. Hamil- 

 ton, it is true (Campi Fhlegrei, p. 63), makes the very well 

 founded remark, that probably this volcano may have been first 

 formed at the time of the earliest of all known eruptions; that 



