364 VIEWS OF NATURE. 



These determinations are, perhaps, deserving of some 

 degree of attention, since they embrace the long period of 

 the great eruptions between 1805 and 1822, and are probably 

 the only measurements hitherto published of any volcano 

 which admit of comparison in all their parts. They prove, 

 that the margins of the crater should be regarded as a much 

 more permanent phenomenon than has hitherto been supposed, 

 from the hasty observations made on the subject; and that 

 this character appertains to them everywhere, and not merely 

 in those instances where, as at the Peak of Teneriffe, and in all 

 the volcanos of the Andes, they evidently consist of trachyte. 

 According to my latest determinations it would seem, that 

 since the time of Saussure, a period of forty-nine years, the 

 north-western margin of Vesuvius has probably not changed 

 at all, and that the south-eastern one, in the direction of 

 Bosche Tre Case, which in 1794 had become 426 feet lower, 

 has since then only altered about 64 feet. 



If, in the newspaper reports of great eruptions, we often 

 find assertions made of an entire change of form in Mount 

 Vesuvius, and if these assertions appear to be confirmed by 

 the picturesque views of the volcano made at Naples, the 

 cause of the error arises from the outlines of the margins of 

 the crater having been confounded with those of the cones of 

 eruption accidentally formed in its centre, the bottom of 

 which has been raised by the force of vapours. A cone 

 of eruption of this kind, formed by the accumulation of 

 masses of rapilli and scoriae, gradually came to view, 

 above the south-eastern margin of the crater, between the 

 years 1816 and 1818. The eruption in the month of 

 February, 1822, increased this cone to such an elevation, 

 that it projected from 107 to 117 feet above the north- 

 western margin of the crater (the Rocca del Palo). This re- 

 markable cone, which was at length regarded at Naples as the 

 actual summit of Vesuvius, fell in with a fearful crash at the last 

 eruption, on the night of the 22nd of October; in consequence 



