SECT. X. AXIS OF ROTATION INVARIABLE. 77 



have happened in the immensity of time. But, had that been 

 the case, its effects would still have been perceptible in the varia- 

 tions of the geographical latitudes. If we suppose that such an 

 event had taken place, and that the disturbance had been very 

 great,' equilibrium could then only have been restored with regard 

 to a new axis of rotation by the rushing of the seas to the new 

 equator, which they must have continued to do till the surface 

 was everywhere perpendicular to the direction of gravity. But 

 it is probable that such an accumulation of the waters would not 

 be sufficient to restore equilibrium if the derangement had been 

 great, for the mean density of the sea is only about a fifth part 

 of the mean density of the earth, and the mean depth of the 

 Pacific Ocean is supposed not to be more than four or five miles, 

 whereas the equatorial diameter of the earth exceeds the polar 

 diameter by about 26% miles. Consequently the influence of the 

 sea on the direction of gravity is very small. And, as it thus 

 appears that a great change in the position of the axis is incom- 

 patible with the law of equilibrium, the geological phenomena 

 in question must be ascribed to an internal cause. Indeed it is 

 now demonstrated that the strata containing marine diluvia, 

 which are in lofty situations, must have been formed at the 

 bottom of the ocean, and afterwards upheaved by the action of 

 subterraneous fires. Besides, it is clear, from the mensuration 

 of the arcs of the meridian and the length of the seconds' pen- 

 dulum, as well as from the lunar theory, that the internal strata 

 and also the external outline of the globe are elliptical, their 

 centres being coincident and their axes identical with that of the 

 surface a state of things which, according to the distinguished 

 author lately quoted, is incompatible with a subsequent accom- 

 modation of the surface to a new and different state of rotation 

 from that which determined the original distribution of the com- 

 ponent matter. Thus, amidst the mighty revolutions which 

 have swept innumerable races of organized beings from the earth, 

 which have elevated plains and buried mountains in the ocean, 

 the rotation of the earth and the position of the axes on its sur- 

 face have undergone but slight variations. 



The strata of the terrestrial spheroid are not only concentric 

 and elliptical, but the lunar inequalities show that they increase 

 in density from the surface of the earth to its centre. This 

 would certainly have happened if the earth had originally been 



