in October, 1822. 179 



in those whose course has been rapid, until it issues at last in 

 clouds from the ragged edges of the stratum at the margin of 

 the great opening. 



„ The great cone of Vesuvius has lost considerably in height. 

 A very large excrescence on the south side, resulting from the 

 accumulated ejections of three or four minor mouths, and forming 

 its most elevated point, fell in during one of the most violent con- 

 vulsions of the last eruption ; so that the opposite or north side 

 of the crater is now the highest peak of the cone. By baro- 

 metrical measurement I find it to be 3829 feet above the sea. 

 The lowest part of the ridge, forming the periphery of the 

 crater, is on the east side above Pompeia, and 3346 feet in 

 height. The absolute elevation of the mountain has been di- 

 minished by rather more than 100 feet, M'hile the bulk of the 

 cone has been greatly increased by the lava torrents that 

 clothe its sides, as well as the still greater mass of ejected 

 fragments. 



Amongst the latter products are some few pieces of granite, 

 and of crystalline limestone with mica, Vesuvian, ^-c, pre- 

 cisely similar to the erratic blocks which so frequently occur in 

 the conglomerates of the Monte Somma ; and hence it appears 

 that the explosions of this recent oruptiou have shattered and 

 blown into the air a portion of the strata belonging to that 

 older volcano. But by far the greater number of ejected blocks, 

 with which the slopes of the cone of Vesuvius have been 

 strewed by the late eruption, consist of leucitic lava, and are 

 evidently fragments forcibly torn olT from those currents of an 

 earlier date, whose sections are seen in the broken and preci- 

 pitous cliffs of the crater. Many of these lavas have a highly 

 torrefied aspect. They have obviously undergone a recoction, 

 if the expression is allowable, either from having been exposed 

 for ages to the heat, which, in the centre of the cone, from 

 whence they were probably torn, must have been always 

 intense, or during the period of rejection by the present erup- 

 tion, having perhaps more than once been vomited forth and 

 thrown back again into the burning gulf, before their final 

 hading on the exterior of the cone. These fragments exhibit 



