Intelligence and Miscellaneous Articles,, 237 



PHYSICS OF THE INTERNAL EARTH. 

 BY D. VAUGHAN. 



In 1853 I first attempted to trace the consequences of subter- 

 ranean heat, by taking into consideration some facts and principles 

 which seemed to have received but little attention. The results of 

 my inquiries on the subject were given in a circular in 1854, in a 

 pamphlet in 1856, and in a paper which I sent to the British 

 Association in 1861, and of which an abstract is published in the 

 Reports of the Sections, page 134. In that paper I endeavoured 

 to show that the terrestrial crust, if reposing on lava of a declining 

 temperature, would receive accessions of buoyant solid material, 

 chiefly on such points as extend deep into the fiery menstruum, and 

 that the consequent growth of internal mountains would be inter- 

 rupted only by the occasional movements of vast portions of this 

 light matter to positions much higher than those at which they were 

 first deposited. To the collisions of such rising masses against the 

 weaker parts of the earth's crust I ascribe earthquakes ; but the 

 theory affords a more satisfactory explanation for volcanic phe- 

 nomena. 



Avalanches of siliceous rocks, ascending through buoyancy from 

 deep subterranean peaks or depressions, would lead to important 

 results by conveying heat from a lower to a higher stratum of the 

 internal earth. Owing their solidity to pressure, such stony masses 

 would fuse during the ascent ; and, like our mountain-floods, would 

 erode channels which must for a long period direct them to the same 

 localities. The same spots of the earth's crust, being thus exposed 

 for many ages to the repeated inroads of intensely heated matter 

 from great depths, would be reduced in thickness by the frequent 

 fusion, and would present a weaker barrier to subterranean vio- 

 lence. Such an internal convection of heat would end in perforating 

 the earth's crust and producing an immense lake of lava on its sur- 

 face, were it not for the cooling influence of aqueous action ; and the 

 presence of water on our globe, though tending much to increase 

 the violence of earthquakes and volcanic eruptions, has the effect of 

 confining their ravages within a more limited range. To the 

 absence of water from the moon we may ascribe the enormous 

 diameters of the craters of lunar volcanoes ; while their height is 

 displayed on a far less scale, and there are no long ranges of lunar 

 mountains. On our satellite also volcanoes have for the most part 

 an insular character, conforming little to the linear arrangement so 

 common on the earth ; so that the cooling agency of water appears 

 to have been concerned in producing the vast rents or fissures on 

 which so many volcanic orifices seem to be located. 



Apart from the evidence which the pendulum and geodetic mea- 

 surements give of inequalities on the invisible side of the earth's 

 crust, it can be proved theoretically that they are inevitable in the 

 course of solidification over the molten mass. One source of solid 

 matter light enough to form the external framework of our globe 



