an Eruption of Mount Vefuvius. y g 
of its fall, that it rnuft have been twice as confiderable 
when in the air. 
There are thoufands of very large fragments of dif- 
ferent fpecies of ancient and modern lavas, that lie fcat- 
tered by the late explolions on the cone of Vefuvins, and 
in the vallies at its foot ; but thefe three were the largeft 
of thole we meafured (y) . 
We found alfo many fragments of thofe volcanic 
bombs that burft in the air, as mentioned in the former 
part of this journal; and fome entire, having fallen to 
the ground without burfting. The frefh red-hot and li- 
quid lava having been thrown up with numberlefs frag- 
ments of ancient lavas, the latter were often clofely en- 
veloped by the former; and probably when fuch frag- 
ments of lava were porous and full of air bubbles, as is 
often the cafe, the extreme outward heat, fuddenly rari— 
fying the confined air, caufed an explofion. When thefe 
fragments were of a more compact lava they did not ex- 
plode, but were limply inclofed by the frefh lava, and 
acquired a fpherical form by whirling in the air, or roll- 
ing down the fteep fides of the volcano. 
( y ) We meafured two other {tones in the valley between Somma and Vefu- 
vius; the one was twenty-two feet and a half long, thirteen feet and a half 
broad, and ten feet high; the other, eleven feet and a half high, and feventy-two 
feet in circumference. 
The 
a 
