288 Baron Humboldt on the Stinciiire and Action of' 



In the early stages of our planet, the substances of the interior, 

 still in a state of fluidity, penetrated through the envelope of the 

 earth which was fissured in all parts ; sometimes condensing as 

 masses of veins with a granulated texture, sometimes spreading 

 out into sheets and stratified torrents. The volcanic rocks which 

 the primitive world has transmitted to us, have nowhere flowed 

 in narrow bands like tlie lavas that issue from the volcanic cones 

 existing at present. The mixtures of augite, titanitic iron, 

 glassy felspar, and hornblende, may have been the same at differ- 

 ent periods, sometimes more allied to basalt, and sometimes to 

 trachyte. The cliemical substances, as we learn from the im- 

 portant labours of M. Mitscherlich, and the similarity of the 

 products oi high furnaces, may have been united under a crys- 

 talline form, according to definite proportions. It is not the less 

 true, that substances, composed in the same manner, have ar- 

 rived by very different ways at the earth's surface, whether by 

 being raised up by elastic forces, or by being insinuated through 

 crevices into the strata of the older rocks; in other words, 

 through the already oxidized envelope of our planet, or by issu- 

 ing under the form of lava from conical mountains, which have 

 a permanent crater. If phenomena so different as these be con- 

 founded together, the geognosy of volcanoes is thrown back in- 

 to the darkness, from which numerous comparative experiments 

 have begun gradually to rescue it 



The question has often been asked, What is it that burns in 

 volcanoes ? What is it that produces the heat in them by which 

 the earth and metals are melted and intermingled ? The new 

 chemistry replies : What burns is the earth, the metals, and even 

 the alkalies, that is to say, the metaloids of these substances. 

 The already oxidized envelope of the earth separates the atmo- 

 sphere, rich in oxygen, from the unoxidised inflammable princi- 

 ples which reside in the interior of our planet. Observations 

 made in all countries, in mines, and caves, and which, in concert 

 with M. Arago, I have detailed in a memoir on the subject, 

 prove that, even at a small depth, the earth's heat is much su- 

 perior to the mean temperature of the surrounding atmosphere. 

 A fact so remarkable, and elicited from observations made in al- 

 i»ost every part of the globe, connects itself with what we learn 



3 



