688 GENERAL ANALOGIES. 



resembles the return of venous blood to the 

 heart. The deposition of sedimentary rocks 

 from a state of solution in the water of lakes and 

 seas, is also somewhat analogous to the process 

 of nutrition, by which the composition of animals 

 is renewed ; while the removal of the effete 

 portions of the body by absorption and elimina- 

 tion, is similar to the wearing away of mountains, 

 hills, and elevated plains, by the corroding action 

 of running water and chemical decomposition. 



If then it be true, that the aggregate vital energy 

 of animals and the development of their whole 

 organization, are in proportion to the quantity of 

 caloric they derive from the atmosphere by res- 

 piration, it must be the animating principle. Or 

 if the faculty of sensation be annihilated by the 

 abstraction of animal heat from the nervous sys- 

 tem, it must be the sentient principle. And if 

 the velocity of planets through their orbits di- 

 minish in proportion to their distance from the 

 sun, it is self evident that their lasting motions 

 would very soon come to an end, in the total ab- 

 sence of solar radiation. But as their centrifugal 

 force is maintained by the perpetual radiation of 

 caloric from the centre towards the circumfe- 

 rence of the system, so is the centripetal force 

 by which they are preserved in their respective 

 orbits, maintained by the unceasing flow and 

 pressure of the same great sethereal tide to the 

 solar fountain from which it emanates. 



