TWO ANTAGONIST DOCTRINES OF GEOLOGY. .671 



.because the measures to which he referred were 

 erroneous, would it have been philosophical in him^ 

 to insist that the difference which he found ought 

 to be overlooked, since otherwise we should be 

 compelled to go to causes other than those which 

 we usually witness in action ? Or was there any 

 praise due to those who assumed the celestial forces 

 to be the same with gravity, rather than to those 

 who assimilated them with any other known force, 

 as magnetism, till the calculation of the laws and 

 amount of these forces, from the celestial pheno- 

 mena, had clearly sanctioned such an identification? 

 We are not to select a conclusion now well proved, 

 to persuade ourselves that it would have been wise 

 to assume it anterior to proof, and to attempt to 

 philosophize in the method thus recommended. 



Again, the analogy of astronomy has been re- 

 ferred to, as confirming the assumption of perpetual 

 uniformity. The analysis of the heavenly motions, 

 it has been said, supplies no trace of a beginning, 

 no promise of an end. But here, also, this analogy 

 is erroneously applied. Astronomy, as the science 

 of cyclical motions, has nothing in common with 

 geology. But look at astronomy when she has 

 an analogy with geology ; consider our knowledge 

 of the heavens as a palsetiological science ; as the 

 study of a past condition, from which the present is 

 derived by causes acting in time. Is there then no 

 evidence of a beginning, or of a progress ? What is 

 the import of the nebular hypothesis? A luminous 



