246 
THE GEOLOGTiiT. 
French geologist, M. C'li. St. CJlaire Peville, of wliicli we reproduce 
tlie following extract: — "I (Lm't know Vi'liether you arc already 
aware that the lava of Yetiuviusi, which ran into the Fusso delhi 
Vefraiia in 18-35, was still, here and there, in an incandescent state 
as late as last autumn, and also that this lava has produced, hy 
sul)liination, a notahle quantity {non piccoJa quaniita) of Cntuiunie 
(chloride of lead), of Avhich I send you some samples, as this 
substance has been very rare here since 1822." 
M. Deville remarks tliat these few lines are well worthy of notice, 
for it is certainly a curious fact that the lava which accumulated 
thickly m la Vetrana should preserve, two years and a-half after its 
emission, enough heat to present, here and there, portions in an 
incandescent state. l>ut the presence of cotunnlte, as a production of 
this lava, is not less remarkable. Our readers must not confound this 
rare mineral species with the chloride of lead called Kerasine, formerly 
discovered m the INIendip Hills of Somersetshire, and analysed by 
Berzelius, who found it contained one atom of chloride, and two atoms 
of oxide, of lead. According to M. Ch. Deville, cotunnite has only 
been seen at Vesuvius on three different occasions, and each time 
shortly after some great eruption or marked activity of the volcano. 
It was first oliserved in 1822, shortly after the great eruption of that 
period, and described by Monticelli and (Jovelli as a ncAV mineral 
species ; it was discovered in the higher crater of the volcano. It 
was next seen in 1840, a short time after the great eruption of 1839, 
when Signor Scacchi also discovered this same mineral in the \ipper 
crater of Vesuvius, near the Pimta del Mmtro. Finally, in 1857, the 
last-named geologist remarked the presence of cotunnite in the lava 
emitted a few months before the time of his observation. 
We have received lately from Sicily a fine sample of crystallized sul- 
phur, from the secondary strata of that island. We were astonished, on 
examining this sulphur, to find with what certainty we are able to arrive 
at its geological origin by reasoning from established chemical facts. Some 
months ago, I\I. Berthelot, one of the most distinguished chemists in 
Paris, showed that the metalloid of wliich we speak manifests two 
distinct forms : 1st, cloctro-negativc sulphur, soluble in many dis- 
solvents, but principally in s\d2)hide of carbon, and crystallising in 
octahedrons ; he has also called this variety " Octahedral sulphur.'' 
2nd, electro-positive, or amorphous sulphur, insoluble in suliihale of 
