1d4 M. Humboldt on Volcanoes* [Aug. 



a permanent or in a variable communication between the interior 

 and the exterior of our planet. 



The pressure of elastic vapour forces the melted substances 

 upwards through deep fissures while they are undergoing oxida- 

 tion ; volcanoes, if I may so speak, are intermitting springs of 

 the earth ; the liquid mixtures of metals, alkalies, and earths, 

 which on cooling become currents of lava, flow quietly when 

 they are raised, and find a vent. The ancients imagined, 

 according to Plato's Phadon, that all volcanic cun'ents of fire 

 flowed, in a similar way, from the Periphlegeton. 



It maybe permitted me, perhaps, to add to these considerations 

 one which is still more hazardous. In this interior heat of the 

 earth, indicated by experiments with the thermometer, and by 

 observations on volcanoes, the cause, perhaps, may be found, of 

 one of the most wonderful phsenomena which the examination of 

 fossils presents to us. Tropical forms of animals, arboriform ferns, 

 palms, and bamboo-like plants, lie interred in the cold north, 

 f he primitive world every where shows a distribution of organic 

 forms at variance with the then existing nature of the cli- 

 mate. In order to solve this important problem, several hypo^ 

 theses have been invented ; as the neighbourhood of a comet, 

 the altered inclination of the ecliptic, the increased intensity 

 of the solar light. Neither of these has been sufficient to 

 satisfy at once the astronomer, the natural philosopher, and 

 the geognost. For my part, I leave the axis of the earth un- 

 altered, as well as the hght of the solar disc, by the spots 

 on which, a celebrated astronomer has explained both the ferti- 

 lity and the unfruitfulness of the fields ; but I beheve, that in 

 every planet, independently of its relation to a central body, and 

 of its astronomical situation, various causes exist of the produc- 

 tion of heat ; oxidation, precipitation, and a change in the 

 capacity of bodies ; by increase of electromagnetic charge, by 

 the opening of a communication between the interior and the 

 exterior part of the earth. 



Where the deeply cleft crust of the earth in the primitive 

 World radiated heat from its fissures, whole countries, perhaps, 

 could produce for centuries, palms and arborescent ferns, and sus- 

 tain all the animals of the torrid zone. According to this view, to 

 which I have already alluded in a work just published, " Essai 

 Geognostique sur le Gissement des lloches dans les deux 

 Hemispheres," the temperature of volcanoes would be that of the 

 interior of the earth itself, and the same cause which now occa- 

 sions such dreadful destruction, would once have occasioned, 

 on the newly oxidated crust of the earth, upon the deeply cleft 

 strata of rocks, the most luxuriant growth of plants in every 

 zone. 



Even if any one should be inclined to suppose, in order to 

 fexplain the marvellous distribution of tropical forms in their 



