630 THE UNIVERSE. 



small artificial volcano by mixing together finely powdered 

 sulphur, iron-filings, and a little water. In a short space of 

 time such an amount of chemical action was set up in this 

 mixture that it took fire. According to the professor of the 

 Jardin du Roi, similar phenomena take place in burning 

 mountains. All those who saw this experiment went forth 

 convinced. Buffon himself adopted this hypothesis. " Be- 

 hold/' said this great man, " what a volcano is in the eyes 

 of a master of physics ! " 



Another philosopher, the illustrious Sir Humphry Davy, 

 also proposed a very ingenious chemical theory, too in- 

 genious, perhaps, for which reason it came less into favor 

 than that of Le'mery. Having discovered certain metals, 

 potassium and sodium, which have the singular property of 

 taking fire so soon as they are brought into contact with 

 water, the English chemist supposed that the flames which 

 issue from volcanoes are only the product of the combus- 

 tion of these metals taking place in the depths of the globe 

 when the water reaches them. 



Notwithstanding the great celebrity of its author, this hy- 

 pothesis had only a very brief existence : phenomena so 

 powerful and general could not have their source in local 

 chemical reactions. The geologists of our epoch are almost 

 unanimous in admitting that all volcanic phenomena are to 

 be attributed solely to the central fire of the globe making 

 greater or less efforts to project outwards the superfluity of 

 its incandescent materials. It is certain that this theory ex- 

 plains easily and better than any other what happens during 

 eruptions, and all those who have visited volcanoes admit it 

 without hesitation. 



