the Chemical Theory of Volcanos. 19 



ing to this question it must be considered that many volcanos, 

 like Vesuvius, are met with in sedimentary rocks containing 

 organic matters, and that by their being heated, sal-ammoniac 

 is formed. Therefore, the small quantities of this salt met 

 with in craters or fumaroles may be sufficiently explained by 

 supposing that rocks containing organic remains reach the 

 focus of a volcano. In support of this I allude to the known 

 facts, that among the masses thrown out of Vesuvius, there are 

 not seldom large masses of limestone, which have likely occa- 

 sioned the formation of sal-ammoniac, and that, during vol- 

 canic eruptions, bituminous odours are frequently perceived in 

 the vicinity of the crater. Therefore, the salt just mentioned 

 is, I think, formed in the same way in volcanos as in coal- 

 strata which have been in a state of ignition for a long time. 

 Thus, near Buttmeiler, in the neighbourhood of Saarbrucken, 

 I have found this salt in clefts proceeding from coal-strata 

 which have been burning about 145 years. 



In general, I by no means doubt that powerful chemical 

 actions must take place in the focus of a volcano, in a spot 

 where the strongest agents, such as an enormous compres- 

 sion and heat, are in operation. It is beyond a doubt that, 

 under such circumstances, by the action of different substances 

 on each other, proceeding both from the focus and from sedi- 

 mentary rocks, chemical actions of the most different kinds 

 must be supposed. Therefore, each theory ought to imagine 

 chemical changes in the focus of a volcano ; but the dispute 

 lies between the two suppositions, whether these changes are 

 a consequence of the effects generated by the internal heat of 

 the earth, or whether they cause them. It is only the latter 

 supposition I contest, from considering the lava as a mass al- 

 ready formed in the interior of the earth. The theory sug- 

 gested by myself and by many naturalists, has only to explain 

 the rising of the lava from beneath ; this is the chief question. 

 On the contrary, all chemical actions taking place at the con- 

 tact of lava with vapours, sedimentary rocks, &c, are con- 

 sidered by this theory only as accidental effects, affording cer- 

 tainly the most diversified phenomena, but without influencing 

 in an essential manner the volcanic actions themselves. All 

 imaginable chemical changes must ensue as soon as organic 



