214 TRANSFORMATION AND EQUIVALENCE OF FORCES. 



still-molten matter occupying its interior. However unten- 

 able may be the details of M. Elie de Beaumont's theory, 

 there is good reason to accept the general proposition that 

 the disruptions and variations of level which take place at 

 intervals on the terrestrial surface, are due to the progressive 

 collapse of the Earth's solid envelope upon its cooling and 

 contracting nucleus. Even supposing that volcanic erup- 

 tions, extrusions of igneous rock, and upheaved mountain 

 chains, could be otherwise satisfactorily accounted for, 

 which they cannot; it would be impossible otherwise to ac- 

 count for those wide-spread elevations and depressions 

 whence continents and oceans result. The conclusion to be 

 drawn is, then, that the forces displayed in these so-called 

 igneous changes, are derived positively or negatively from 

 the unexpended heat of the Earth's interior. Such phenom- 

 ena as the fusion or agglutination of sedimentary deposits, 

 the warming of springs, the sublimation of metals into the 

 fissures where we find them as ores, may be regarded as posi- 

 tive results of this residuary heat; while fractures of strata 

 and alterations of level are its negative results, since they 

 ensue on its escape. The original cause of all these 

 effects is still, however, as it has been from the first, 

 the gravitating movement of the Earth's matter towards the 

 Earth's centre; seeing that to this is due both the internal 

 heat itself and the collapse which takes place as it is radiated 

 into space. 



When we inquire under what forms previously existed 

 the force which works out the geological changes classed as 

 aqueous, the answer is less obvious. The effects of rain, of 

 rivers, of winds, of waves, of marine currents, do not mani- 

 festly proceed from one general source. Analysis, neverthe- 

 less, proves to us that they have a common genesis. If we 

 ask, Whence comes the power of the river-current, bearing 

 sediment down to the sea? the reply is, The gravitation of 

 water throughout the tract which this river drains. If we 

 ask, How came the water to be dispersed over this tract? 



