MASS OF THE EARTH. 43 



same adjustment, the same result of a comparison 

 of quantities, manifests itself in the relation 

 which the forces of the organic world bear to 

 the force of gravity. 



The force of gravity might, so far as we can 

 judge, have been different from what it now is. 

 It depends upon the mass of the earth ; and this 

 mass is one of the elements of the solar system, 

 w%ich is not determined by any cosmical neces- 

 sity of which we are aware. The masses of the 

 several planets are very different, and do not ap- 

 pear to follow any determinate rule, except that 

 upon the whole those nearer to the sun appear to 

 be smaller, and those nearer the outskirts of the 

 system to be larger. We cannot see anything 

 which would have prevented either the size or 

 the density of the earth from being different, to 

 a very great extent, from what they are. 



Now, it will be very obvious that if the inten- 

 sity of gravity were to be much increased, or 

 much diminished, if every object were to become 

 twice as heavy or only half as heavy as it now is, 

 all the forces, both of involuntary and voluntary 

 motion which produce the present orderly and 

 suitable results by being properly proportioned 

 to the resistance which they experience, would 

 be thrown off their balance ; they would produce 

 motions too quick or too slow, wrong positions, 

 jerks and stops, instead of steady, well conducted 

 movements. The universe would be like a ma- 



