228 Dr Daubeny on the Spring at Torre del Annunziata. 



tend to renew on the present occasion the discussion that has 

 been carried on in the Philosophical Transactions between Dr 

 John Davy and myself relative to that subject ; a discussion, 

 however, which, on whatever side the advantage may be consi- 

 dered to rest, I shall not regret having provoked, if it has had 

 the effect of bringing the subject of the gases disengaged from 

 thermal waters and from volcanos more prominently forward. 



Without, however, entering into any further dispute with 

 respect to the manner in which the evolution of air, from the site 

 of the volcanic island off the coast of Sicily, may have been 

 brought about, I will just remark, that the constitution of that 

 which was evolved is such as to imply the previous abstraction 

 from it of a part of its oxygen. Now, if the same fact can be 

 established in almost every case in which air is evolved from a 

 source, the connection of such phenomena with some process of 

 oxidation seems fairly established. 



To refer this abstraction of oxygen in general to animal or 

 vegetable putrefaction is plainly impossible; and hence most 

 persons will be led to seek for some processes or other connected 

 with, or analogous to, combustion, as the most likely of any with 

 which we are acquainted to have occasioned it. 



And, if this be conceded, I am quite ready to wave all far- 

 ther demands upon the acquiescence of my readers ; for, with 

 respect to the particular hypothesis which I have myself advo- 

 cated, in which the basis of the earths and alkalies are assumed 

 to be the substances thus oxidated, I only claim for it the merit 

 of explaining the phenomena, which it appears to me cannot be 

 shewn to belong to the rival theory embraced by Cordier. 



Whilst, however, I still object to the mode in which Dr Davy 

 conceives the nitrogen emitted round the volcanic island to have 

 been deprived of so large a proportion of its accompanying oxy- 

 gen, inasmuch as (waving other considerations) the same explana- 

 tion could not be extended to the other analogous cases, I am 

 less indisposed to admit that the gas may in many instances have 

 been separated from the water, and not derived from an indepen- 

 dent source. 



Perhaps the gas evolved in the case stated by Dr Davy pre- 

 sents the greatest difficulties to such a solution, for it does not 

 seem clear why the water, which had disengaged a portion of its 



