320 OUTLINES OF NATURAL PHILOSOPHY. 



rior regions of the air, sets from the equator to- 

 ward the poles. 



. In former ages, however, if the changes 

 that have happened on the surface, or in the 

 interior of the Earth, have been as great as 

 some Geologists suppose, the change in the 

 diurnal rotation may have been very consider- 

 able. 



If the ocean once stood at the height of 1 5,000 feet 

 above its present level, a quantity equal in bulk to 

 a 440th part of the whole Earth, must have passed 

 from being above the level of the present sea to be 

 under it. If the mean density of water were the 

 same with that of the Earth, it may be calculated 

 easily, that the time of the diurnal revolution must, 

 on this account, be shortened by 5^.682. As the 

 Earth's mean density is to that of water nearly as 

 4?.71 to 1, this acceleration is reduced to 1m 



325. The changes on the surface, or in the in- 

 terior of the Earth, may have produced great 

 variations in the position of the Earth's axis, 

 relatively to the Earth itself, as well as in the 

 lime of the diurnal rotation. 



If the Earth had originally a very irregular figure ; 

 and if, as above suggested, it has acquired its pre- 



sent 



