GK!)(;i\(»STI(' I'llKVOMKXA. 203 



liquid tiuids, of hot mud, aud of those heated and molten 

 earths which become sohdified into crystalline mineral masses. 

 Modern geognosy, the mineral portion of terrestrial physics, 

 has made no slio;ht advance in having investisfated this con 

 nection of phenomena. This investigation has led us away 

 from the delusive hypothesis, by which it was customary for- 

 merly to endeavor to explain, individually, every expression of 

 force in the terrestrial globe : it shows us the connection of 

 the occurrence of heterogeneous substances with that which 

 only appertains to changes in space (disturbances or eleva- 

 tions), and groups together phenomena which at first sight 

 appeared most heterogeneous, as thermal springs, eilusion of 

 carbonic acid and sulphurous vapor, innocuous salses (mud 

 eruptions), and the dreadful devastations of volcanic mount- 

 ains.* In a general view of nature, all these phenomena are 

 fused together in one sole idea of the reaction of the interior 

 of a planet on its external surface. We thus recognize in the 

 depths of the earth, and in the increase of temperature with 

 the increase of depth from the surface, not only the germ of 

 disturbing movements, but also of the gradual elevation of 

 whole continents (as mountain chains on long fissures), of vol- 

 canic eruptions, and of the manifold production of mountains 

 and mineral masses. The influence of this reaction ot" the 

 interior on the exterior is not, however, limited to inorganic 

 nature alone. It is highly probable that, in an earlier world, 

 more powerful emanations of carbonic acid gas, blended with 

 the atmosphere, must have increased the assimilation of car- 

 bon in vegetables, and that an inexhaustible supply of com- 

 bustible matter (lignites and carboniferous formations) must 

 have been thus buried in the upper strata of the earth by the 

 revolutions attending the destruction of vast tracts of forest. 

 We likewise perceive that the destiny of mankind is in part 

 dependent on the formation of the external surface of the earth, 

 the dfi-ection of mountain tracts and high lands, and on the 

 distribution of elevated continents. It is thus granted to the 

 inquiring mind to pass from link to link along the chain of 

 phenomena until it reaches the period when, in the solidifying 

 process of our planet, and in its first transition from the gas- 

 eous form to the agglomeration of matter, that portion of the 

 inner heat of the Earth w^as developed, which does not belong 

 to the action of the Sun. 



* [See Manteirs Wonders of Geology, 1848, vol. i., p. .34, 3(j, 10.5; 

 also Lyell's Principcs of Geology, vol. ii., and Daubeney On Volcanoes, 

 ^d ed., 1848. Part ii.. cli. xxxii., xxxiii.] — 2r. 



