7S Reply of Dr. Dauheny to Prof. Bischof 



Art. Y. — Reply ofBv. Daub en y to Prof Bischof s Objections to 

 the Chemical Theory of Volcanos. — Edinb. New Phil. Jour, 

 for April, 1839. 



Prof. Daubkny after referring to an article of his in the Edinb. 

 Jour, for 1S32, aud to the article Yolcanic Geology, in the Ency- 

 clop. Metro., proceeds to vindicate his own views in regard to 

 the chemical theory of volcanos, by replying as follows, to the 

 objections against it. 



IstObjection.-lt isnot true that volcanos are always near the sea. 



Pesckan, in the cenire of Asia, is 260 geographical miles from 



any'great sea, and yet has given rise to streams of lava within the 



period of our history. It also lies 25 geographical miles from the 



lake of Timartu or Issikul, which is not twice as large as the lake 

 of Geneva. 



The volcano of Turfan also is surrounded by very inconsidera- 

 ble lakes. 



Answer, — The general connection of volcanic action with, or a 

 proximity to, large masses of salt or fresh water, is all that seems 

 required by the conditions of our theory. 



Now, in proof of this general proximity, it may be remarked, 

 that out of a catalogue of no less than;;163 active vents enume- 

 rated by M. Arago, as occurring in various parts of the known 

 world, all excepting two or three in different parts of America, 

 and about the same number of which we possess very imperfect 

 information, in Central Asia, are within a short distance at least 

 of the ocean. It is even found that the very excepted cases, when 

 examined, tend to confirm the rule, being so situated, that their 

 connection, either with the ocean or with inland seas that may 

 supply its place, becomes a matter of fair inference. In proof of 

 this, we need only refer to the descriptions given by Humboldt of 

 Jorullo ; from which it appears, that distant as this mountain may 

 be both from the Atlantic and Pacific Oceans, it is nevertheless 

 connected with one or both through the medium of a chain of 

 volcanic eminences ; and even the volcanos of Tartary, whose 

 existence in an active condition is more problematical, may be 

 connected with some of those extensive salt lakes which seem to 

 abound in the depressed portion of Central Asia. 



2d Objection. — Atmospheric air cannot gain admittance to the 

 focus of a volcano, because there must be an enormous force act- 



