Origin of Mount Etna, 39t 



as a whole, of a tumefaction, which, in elevating the entire mass 

 of the central gibbosity, has communicated to the lateral por- 

 tions an oscillatory movement. The surface formerly nearly flat, 

 and now replaced by this gibbosity, has been first repeatedly 

 fractured in various lines having a nearly constant direction. 

 The melted matters have been poured out through the fissures 

 thus produced, and their fluidity must have been nearly per- 

 fect, for they have flowed through rents of very inconsider- 

 able breadth. These products were then spread on both sides 

 of the fissures, in thin and uniform masses, similar to those 

 composed of basalt, which in so many diff'erent countries, and 

 especially in Iceland, are superimposed above one another, form- 

 ing vast plateaus whose surface remained always nearly hori- 

 zontal, in consequence of the subdivision of successive lines of 

 eruption on an extensive space. The eruptions were, like those 

 of the present day, accompanied by disengagements of elastic 

 fluids, which, issuing like the lava itself from the whole extent 

 of the fissures, carried along with them scoriae and cinders. 

 These scoriae and cinders falling back like rain, both on the 

 lava and on the neighbouring spots, produced those uniform 

 layers of fragmentary substances, which alternate with the lay- 

 ers of melted matters. But at one period, it would appear 

 that the internal agent which had already fractured so frequent- 

 ly the solid surface, having doubtless exerted an extraordinary 

 energy, broke up that surface, upraised it, and since that time 

 Etna has existed. 



The " soulevement ■" does not seem to have operated here 

 with the same degree of simplicity as in the localities where it 

 has given rise to regular craters of soulevement, such as that of 

 the island of Palma, or the circular walls of Teneriffe and the 

 Somma. The effort which has elevated the gibbosity of Etna, 

 seems to have acted, not at one single and central point, but in 

 a straight line, represented by the axis of the ellipse of which 

 the southern, northern, and eastern flanks of the Val del Bove 

 form part ; and it appears to have acted unequally on different 

 parts of this straight line, so that its western extremity, which 

 corresponds to the present volcanic vent, has been elevated more 

 than all the rest. A similar soulevement could not take place 

 without rupturing the masses so elevated, and the rents neces- 



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