298 Dr Daubeny on Volcanos, 



under the equator in the New World, and according to Bis- 

 chof, in those near the Rhine. 



Answer, I believe, that muriatic acid will be found pretty 

 constantly present in volcanos now in activity. Sir H. Davy 

 found it at Vesuvius on both the occasions he visited that vol- 

 cano, viz. 1815 and 1829. I myself in 1834, detected it there 

 in great abundance; and in 1825, found it at the Solfatara, 

 in the Island of Vulcano, and near Mount Etna. It has been 

 discovered also in the volcanos of Iceland ; in those of Java, 

 at Mount Idienne ; and of South America, at Purace. The 

 sal-ammoniac which so abounds in the volcanos of Tartary, 

 shews, that it is also present there ; and the existence of it in 

 the trachytic rock of the Puy de Sarcouy in Auvergne, proves, 

 that it was a concomitant of volcanic action in days that have 

 gone by. 



All therefore that Bischof is warranted in inferring from its 

 absence in the case of the volcanos of the Rhine and Equato- 

 rial America, is, that it ceases to be disengaged when the ac- 

 tion becomes languid or extinct. Now there are many ways of 

 accounting for this. In the first place, granting the acid to be 

 derived from the sea-salt present in the water which originated 

 the volcanic action, it would cease to be generated when this 

 fluid no longer obtained admission ; or, when the heat was in- 

 adequate to cause the union of the alkali of the sea-salt with 

 the earths present ; and even if it were still generated, it might 

 be prevented from rising to the mouth of the crater, by com- 

 bining in its way with the calcareous rocks through which it 

 had to pass. Hence the carbonic acid, which Professor Bis- 

 chof remarks as so abundantly evolved by the volcanos of the 

 Rhine, may perhaps represent an equal volume of muriatic 

 acid, by whose agency it had been evolved from the limestones 

 that contained it. 



Thus have I replied seriatim to all the objections, which an 

 acute and learned opponent has been able to adduce against 

 the chemical theory of volcanos ; and having done so, might be 

 expected perhaps to proceed to some remarks on the one to 

 which he himself has given the preference. 



But in order not to occupy too much of your space, I will 

 jnerely here remark, that Professor Bischof appears (at least in 



