390 M. L. Elie de Beaumount on the Structure and 



of lava which enter into the composition of the flanks of the Vol 

 del Bove present horizontal dimensions comparable to those of 

 the largest currents which have been thrown up by volcanos of 

 the present day. Their mineralogical composition is almost 

 identical with that of the lavas of modern Etna ; the laws de- 

 duced from the above-mentioned table arc therefore applicable 

 to them. We ought, then, to expect that the volcanic products 

 formed on declivities having extremely diflerent inclinations, 

 should have acquired also very different structures; and as we 

 perceive that the structures of the layers which are nearly hori- 

 zontal, of those whose inclination gradually increases, and even 

 of those which are inclined on extensive surfaces at an angle of 

 from 25° to 80°, have in all respects precisely the same characters, 

 >ve are warranted in drawing the conclusion that the difference 

 which exists in their present positions is the consequence of the 

 movement which the layers of the one series or the other have 

 undergone since the period of their solidification. 



It only remains to determine which of the layers have changed 

 their position, — those which are horizontal or those which are 

 inclined. Now, if we look in the table for the place where the 

 layers of the Val del Bove could be interposed, without, from 

 their general characters, forming a considerable anomaly, we find 

 that they could only be placed in the portion comprising the 

 currents which have stopped on very gently inclined slopes. 

 From this it is evident that the layers whose original inclination 

 is changed, are those which are at the present day highly in- 

 dined ; and that those which are nearly horizontal have, on the 

 contrary, preserved in relation to the horizon nearly their origt- 

 Hal position. 



The considerations of which I have now given the analysis 

 unite with those which I have above simply mentioned, in prov- 

 ing that the portions of the layers of the escarpment of the Vol 

 del Bove which are highly inclined, are not at present in the po- 

 sition in which they were originally accumulated. 



The inclination which has been acquired by some parts of 

 this system of beds, has not been a simple movement of pres- 

 sure, or the effect of dislocations purely local. It is sufficient 

 to glance at the panoramas I have sketched, in order to perceive 

 that the inclinations present a disposition, indicative, when taken 



2 



