PT. i. Astronomy and Geology compared. 39 



remember, as stated above, that the whole mass of 

 our own Globe rushes through space with a velocity 

 exceeding eighteen miles a second ; and we may 

 estimate the exquisite nicety of adjustment between 

 these two opposing forces, when we consider that 

 they are so accurately balanced as to produce, as I 

 have stated above, the annual revolution of the 

 Earth round the Sun to the fraction of a second 

 of time. The same effects result from the same 

 causes throughout the whole Solar System ; every- 

 where we see the law of gravity controlling the 

 centrifugal force, and compelling the planet to 

 describe the elliptical curve marked out for it 

 in space. 



What are these two forces ? whence do they 

 spring? how are they governed? how modified so 

 that their combined operation produces so harmo- 

 nious an effect ? We cannot tell ; human reason only 

 enables us to trace secondary causes to their origin 

 in the First Great Cause. These secondary causes 

 we call laws, but that term cannot explain their 

 origin. The force of gravity is a law of nature 

 which, as far as we know, is universally operative, 

 but so is the law of centrifugal force, which is 

 directly opposed to the other. What is the power 



