42 SIXTH REPORT — 1836. 



scribed, as occurring near Inverkeithing in Scotland, by the Rev. 

 W. Robertson*, and I have been informed of a third in Shrop- 

 shire by Mr. Murchison. 

 Oxygen. In one or two cases oxygen is said to predominate in the air 



evolved, as Robiquet says is the case at Vichy ; but as he adds, 

 that it is only found, after the water has been standing in the 

 reservoir long enough to be covered by a vegetable slime, I 

 conceive this gas to have arisen from the decomposition of car- 

 bonic acid within the tissue of the plant, under the influence of 

 solar light. 

 Carburetted Carburetted hydrogen has in many instances been observed 

 ydrogen. ^.^ issue from springs, as well as from clefts in tlie earth, as at 

 the Pietra Mala on the Apennines, and at St. Barthelemi near 

 Grenoble, where the gas, when once kindled either by accident 

 or design, maintains a continued flame, until pains are taken to 

 extinguish it. 



It has also been observed in many parts of the world to issue 

 copiously from salt springs, as at Medonia in the State of New 

 York, in China, &c. ; and a curious proof that the salt, with 

 which these springs are impregnated, had been deposited under 

 pressure, is afforded by the fact, that at Wielichza in Gallicia its 

 cavities contain carburetted hydrogen in a condensed state, so 

 that on immersing a lump of this salt in water, a series of small 

 detonations is heard during its solution, in consequence of the 

 sudden expansion of the gas on escaping from its prison. 



It is an interesting circumstance, to find this phasnomenon 

 conthuiing in the very spots, in which it was observed during 

 the periods of Grecian history. 



I have quoted in another placef , an instance of its occurrence 



among the Chimariot mountains of Albania, where ancient 



writers speak of a nympheum as existing, by which they meant 



to express, that a stream of inflammable gas had there been 



obsei'ved. 



Suipim- The same permanency seems also in some cases to be the 



retted by- attribute of sulphurcous waters ; for the hot springs of Bithj?^- 



'Jgei- jjjj^^ which modern travellers describe as impregnated with 



sulphuretted hydrogen, appear from the accounts of Greek 



writers I to have been similarly constituted nearly two thousand 



years ago. 



These, however, which are thermal sulphureous springs, pro- 



* Edinburgh New Philosophical Journal, 1829. 

 f Memoir on the Bath Waters above quoted. 



t See the Poem " IIsj/ t« sv Uvdiuii Qi^fAcc" extracted from the Greek 

 Anthology in my Description of Volcanos, 8vo, 1826. 



J 



