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mine.] Nevertheless the above observations upon the temperature of lava, 

 and the comparatively small depth, forty miles, at which condensation of 

 rock would be capable of producing it, together with the small amount of 

 condensation necessary, viz., 0.041, render it quite probable that fusion may 

 have ensued in the deep interior without the necessity of a greater amount of 

 condensation than such materials might be supposed capable of under the 

 enormous pressure to which they would be subjected, even allowing for the 



increase of the melting point under pressure It will be noticed 



that a compression less than would be requisite of itself to produce the 

 necessary density would be sufficient to produce the requisite temperature for 

 fusion. But while any stratum was cooling by the conduction upwards of its 

 own heat of compression, it would be receiving heat from regions below, 

 where, so long as condensation was going on, the materials would grow hot- 

 ter and hotter. It seems therefore possible that the upper layers, forming 

 what we call the crust of the earth, may have received sufficient heat supplied 

 from below to render the temperature gradient at the present time higher 

 than it was originally, and that even those Archean rocks, which are by many 

 thought to have been once melted, do not necessarily prove that the earth 

 was not built of cold meteorites. 



The presence of water upon the earth has to be accounted for, and the 

 meteoric theory does not easily lend itself for this purpose. Not only is water 

 present in the ocean and in the atmosphere, but also in a state of solution in 

 the interior, as is testified by the enormous amount of steam emitted by vol- 

 canoes, and by cooling lava. It does not seem possible that molten rock can 

 imbibe water from without, because it would be driven away instead of 

 attracted, since the superficial tension of a substance diminishes as the tem- 

 perature rises. 



The problem of accounting for the vast quantities of steam emitted 

 by lavas is shared by both theories. Under the hypothesis of a molten 

 earth, steam must have been absorbed either in the original molten 

 state or during the later stages of segregation and ascent, neither of 

 which alternatives seems to be free from difficulties. Under the 

 meteoric hypothesis, it is assumed that hydrogen, carbon dioxide, 

 carbon monoxide, and nitrogen were carried into the whole body of 

 the earth by the infalling matter in some such degree as they are 

 brought to the surface now by meteorites, and that these gases, joined 

 with oxygen derived from the partial reduction of the oxides of the 

 meteoric matter when subjected to the high temperatures of the 

 interior, were extruded by volcanic and similar means and gave rise to 

 the ocean and atmosphere. Under this hypothesis the volcanic gases 

 are regarded as mainly original and as merely lingering expressions 



