40 SIXTH REPOKT — 1836. 



at Bath, ami by Pearson at Buxton, before the commencement 

 of the present century. 

 In iiicimal Morc recently it has been observed issuing from almost all 

 hill iig:,. the sulphureous thermal waters of the Pyrenees*; and I have 

 shown, that not only has it in many instances been mistaken 

 for carbonic acid, but also that it is commonl)^ evolved where- 

 ever thermal waters existf. 



Even when the prevailing gas emitted is carbonic acid, I find 

 that a small quantity of residuary air is present, which consists 

 in general of oxygen and niti'ogen, but with a much smaller 

 proportion of the former than that present in the atmosphere. 



The volcanic district of Ischia affords the only example that 

 has occurred to me, of a number of thermal springs lying to- 

 getliei*, not one of which evolves nitrogen^. 



In this case, however, we may remark, that no kind of air 

 whatever is emitted from the waters, which therefore would 

 seem to derive their heat, not from any volcanic processes going 

 on at present, but from their contiguity to a mass of rock heated 

 by antecedent eruptions. 



In corroboi'ation of this view I may state, that several springs 

 on the skirts of Vesuvius, where volcanic operations are actually 

 proceeding, give out nitrogen, though in much smaller quantity 

 than they do carbonic acid ; as for example, the thermal water 

 of Torre del Annunziata, and the cold spring of Castellamare. 



From the Thermals connected with extinct volcanos, azote is 

 emitted, though for the most part in inferior quantity, than it is 

 from springs associated with primary, or with intrusive rocks of 

 older formation. 

 Its amount. The quantity of this gas returned to the atmosphere through 

 the medium of thermal waters is evidently considerable. I 

 measured that emitted from the King's Bath, in the city of 

 Bath§, nearly every day for a month dm'ing the autumn of 1833, 

 and found that its average quantity was 267 cubic inches per 

 minute, or 222 cubic feet in the 24 hours. 



The gas consisted of 97 per cent, of nitrogen, and of 3 per 

 cent, of oxygen, with a variable quantity of carbonic acid. 

 Since this period, the sinking of a well in a remote quarter of 

 the town through the lias to the depth of 250 feet, from which 

 water rose of a temperature but little inferior to that of the 



• Anglada, Mcmoires. 



t On Hot Springs and their connexion with Volcanos, Edinhuryh New 

 Philnsophical Journal for 1832. 



X Daubenv, on a Spring at Torre del Annunziata near Naples. 



§ Sec my l'a|iur on the quantity and quality of the Gases disengaged from 

 the Thermal Springs at Bath, Philosophical Transactions, 1834. 



