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HUTTONIAN THEORY. 



427 



c?77. Mr Kirwan's fecond objedlion is founded 

 X)n the mlfapprehenfion of a well-known 



fad 



the 



a 



move 



equator ; and thofe which defcend from a higher to a 

 lower level, dlfturb the earth's rotation, much more in 

 confequence of their horizontal, than of their perpendi- 

 cular motion. The Ganges, for inflance, though its 

 fource is probably elevated no lefs than 7000 feet above 

 the level of tlie fea, tends to retard the earth's rotation, 

 by bringing its waters, and the mud contained in them, 

 from the parallel of 31^ to that of 22°, and fo increa- 

 iing their diftance from the earth's axis by more than 

 xVth part. TIad the Ganges flowed towards the north, 



as the Nile does, its effcft would have been juil the -con- 

 trary. 



In the fame manner, a ilone defcending from the ton 

 of a mountain, may accelerate or retard the earth's rota- 

 tion, according to the direction in which it defcends. If 

 it defcend on the fide of the elevated pole, it will then 



r 



produce acceleration, bccaufe its diftance from the axis 

 will be diminiftied ; but if it defcend on the fide of the 

 ^epreffed pole, and if the direftion in which it is 

 ved, be over a line lefs inclined, than a line drawn from 

 the fame point to the depreifed pole, it will then pro- 

 duce a retardation, becaufe its diftance from the axis 

 v/ill be increafed. 



Let us fuppofe, for example, that the top of Mount 

 Blanc is in latitude 45"^ 49', and that its height is 2430 

 toifes above the level of the fea. The point at which 



w 



a line drawui from the top of this mountain, narallel to 



mo 



