34 COSMOS. 



tion. In a portion of my work, which treats of volcanic pheno- 

 mena, I cannot wholly pass in silence those problems, which 

 have been suggested by other inquirers in reference to the 

 currents pervading the general fluid in the interior of our 

 planet, or the probable or improbable periodically ebbing 

 and flowing movement in individual and imperfectly filled 

 basins, or the existence of portions of space, having a very 

 low specific gravity and underlying the upheaved mountain 

 chains 29 In a work devoted to cosmical phenomena 

 no question should be overlooked on which actual observa- 

 tions have been instituted, or which may seem to be eluci- 

 dated by close analogies. 



b. The Existence and Distribution of Heat in tlie interior of 

 our Globe. 



(Expansion of the Delineation of Nature, 

 Cosmos, vol. i, pp. 160 168.) 



Considerations regarding the internal heat of our earth, 

 the importance of which has been greatly augmented by the 

 connection which is now generally recognised to exist be- 

 tween it and phenomena of upheavals and of volcanic action, 

 are based partly upon direct, and therefore incontrovertible 

 measurements of temperature in springs, borings, and sub- 

 terranean mines, and partly upon analytical combinations 

 regarding the gradual cooling of our planet, and the influence 

 which the decrease of heat may have exercised in primeval 

 ages upon the velocity of rotation and upon the direction 

 of the currents of internal heat. 30 The figure of the com- 

 pressed terrestrial spheroid is further dependent upon the 

 law, according to which density increases in concentric 

 superimposed non-homogeneous strata. The first or experi- 

 mental, and therefore the more certain portion of the in- 

 vestigation to which we shall limit ourselves in the present 

 place, throws light only upon the accessible crust of the 

 earth, which is of very inconsiderable thickness, whilst the 



- 9 See Petit sur la latitude de I' Observatoire de Toulouse,^ la density 

 moyenne de la cliaine des Pyrenees, et la probabilite quil existe un vide 

 sous cette cliaine, in the Comptes rendus de I'Acad. des Sc., t. xxix, 1849, 

 p. 730. 



80 Cosmos, vol. i, p. 1 69. 



