THE DEDUCTIVE METHOD. 547 



phenomena of nature is determined or modified. Yet 

 how could we ever have ascertained the combination 

 of forces upon which the motions of the earth and 

 planets are dependent, by merely comparing the orbits^ 

 or velocities, of different planets, or the different 

 velocities or positions of the same planet ? Notwith- 

 standing the regularity which manifests itself in those 

 motions, in a degree so rare among the effects of a 

 concurrence of causes ; although the periodical recur- 

 rence of exactly the same effect, affords positive proof 

 that all the combinations of causes which occur at all,, 

 recur periodically; we should never have known what 

 the causes were, if the existence of agencies precisely 

 similar on our own earth had not, fortunately, brought 

 the causes themselves within the reach of experimenta- 

 tion under simple circumstances. As we shall have 

 occasion to analyze, further on, this great example of 

 the Method of Deduction, we shall not occupy any 

 time with it here, but shall proceed to that secondary 

 application of the Deductive Method, the result of 

 which is not to prove laws of phenomena but to 

 explain them. 



2 N 2 



