594 HISTOEY OF GEOLOGY. 



The analogy of other sciences has been referred to, as sanctioning 

 this attempt to refer the whole train of facts to known causes. To 

 have done this, it has been said, is the glory of Astronomy : she seeks 

 no hidden virtues, but explains all by the force of gravitation, which 

 we witness operating at every moment. ' But let us ask, whether it 

 would really have been a merit in the founders of Physical Astronomy, 

 to assume that the celestial revolutions resulted from any selected 

 class of known causes ? When Newton first attempted to explain the 

 motions of the moon by the force of gravity, and failed 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 phenomena, 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 philoso- 

 phize in the method thus recommended. 



Again, the analogy of Astronomy has been referred to, as confirm- 

 ing 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 where she has an 

 analogy with Geology ; consider our knowledge of the heavens as a 

 palpetiological science ; as the study of a past condition, from which 

 the present is derived by causes acting in time. Is there then no evi- 

 dence of a beginning, or of a progress ? What is the import of the 

 Nebular Hypothesis ? A luminous matter is condensing, solid bodies 

 are forming, are arranging themselves into systems of cyclical motion ; 

 in short, we have exactly what we are told, on this analogy, we ought 

 not to have ; the beginning of a world. I will not, to justify this 

 argument, maintain the truth of the nebular hypothesis ; but if geo- 

 logists wish to borrow maxims of philosophizing from astronomy, such 

 speculations as have led to that hypothesis must be their model. 



Or, let them look at any of the other provinces of palastiological 

 speculation ; at the history of states, of civilization, of languages. We 



