Reply of Dr. Dauheny to Prof. Bischof. 83 



^th Objection. — If, according to Gay-Liissac, the hydrogen of 

 the decomposed water goes to form muriatic acid with chlorine, 

 the above mentioned acid ought to be general in volcanos. Now, 

 it is wanting, according to Boussingault, in the volcanos under 

 the equator in the New World, and according to Bischof, in those 

 near the Rhine. 



Anstver. — 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-ammonia which so abounds in the volcanos of Tartary, 

 shows, 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 Equatorial 

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

 comes languid or extinct. Now there are many ways of account- 

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

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

 canic action, it would cease to be generated when this fluid no 

 longer obtained admission ; or, when the heat was inadequate 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 pre- 

 vented from rising to the mouth of the crater, by combining in 

 its way with the calcareous rocks through which it had to pass. 

 Hence the carbonic acid, which Professor Bischof 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 hmestones 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 ex- 

 pected perhaps to proceed to some remarks on the one to which 

 he himself has given the preference. 



