Sir william Hamilton’s Account of 
In another of my excurfions to Mount Vefuvius lafk 
year, I picked up fome fragments of large and regular 
cryftals of clofe-grained lava or bafalt, the diameter of 
which, when the prifms were complete, may have been 
eight or nine inches. As Vefuvius does not exhibit any 
lava’s regularly cryftallized, and forming what are vul- 
garly called Giants Caufeways (except a lava that ran 
into the fea near Torre del Greco in 1631, and which in 
a fmall degree has fuch an appearance), this difcovery 
gave me the greateft pleafure (f> . 
After this flight fketch of the molt remarkable events 
on Vefuvius iince the year 1767, which I flatter myfelf 
will not be unacceptable, as it may ferve to conneff what 
I am going to relate with what has already been commu- 
nicated to the Society in my former letters on the fame 
fubje6t, I come to the account of the late eruption, which 
affords indeed ample matter for curious {peculation. 
{/) As the fragments of bafalt columns, which I found on the cone of Ve- 
fuvius, had been evidently thrown out of its crater, may not lava be more fub- 
jecl to cryftallize within the bowels of a volcano than after its emiflion, and 
having beenexpofed to the open air? And may not many of the Giants Caufe- 
ways, already difcovered, be the nuclei of volcanic mountains, whofe lighter 
and lefs folid parts may have been worn away by the hand of time ? Mr. fau- 
j eis de st. fond, in his curious book lately publifhed, and intitled, “ Re- 
“ cherches fur les Volcains eteints du Vivarais et du Velay,” gives (p. 286.) an 
example of bafalt columns, that are placed deep within the crater of an extin- 
guifhed volcano. 
As 
