246 



THE GEOLO&Ts^T. 



French, geologist, Isl. Cli. St. Claire Deville, of wliicli we reproduce 

 tlie folloYving extract : — " I don't know wlietlier you are already 

 awa]'e that the lava of Vesuvius, v\diich ran into the Fosso della 

 Vetrana in 1855, v\^as still, here and there, in an incandescent state 

 as late as last autumn, and also that this lava has produced, hy 

 sublimation, a notable ciuantity {non jnccoJa quanfifa) of Cotunniie 

 (chloride of lead), of vvdiicli I send yon some ^ samples, as this 

 substance has been very rare here since 1822." 



M. Deville remarks that these few lines are well vfortliy of notice, 

 for it is certainly a curious fact that the lava which accumulated 

 thickly in la Vetrana should preserve, two years and a-half after its 

 emission, enough heat to present, here and there, portions in an 

 incandescent state. But the presence of cotunnite, 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 in the Mendip 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 observed in 1822, shortly after the great eruption of that 

 period, and described by Monticelli and Covelli as a new^ 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 upper 

 crater of Vesuvius, near the Punta del Mauro. Finally, in 1857, the 

 last-named geologist remarked the presence of cotunmte 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 

 uiouths ago, ]\I. Bertlielot, one of the most distinguished chemists in 

 Paris, showinl that tlio luetalloid of which we speak manifests two 

 distinct forms : is'i, ('lcct^o-negati^'u sulpliur, sohdjle in many dis- 

 solvents, l)ut priucipa.lly in sulphid!' d' carbon, and crystallising in 

 (M'taluMlrons ; lu« has also called ibis variety " Octahedral sulphur." 

 I'nd, elect ro-positivo, or auiorplious sulpliur, iiisoluLlr in sulphate of 



