26 INDUCTION". 



from the indications exhibited by the corpse, the 

 presence or absence of signs of struggling on the 

 ground or on the adjacent objects, the marks of blood, 

 the footsteps of the supposed murderers, and so on, 

 proceeding throughout upon uniformities ascertained 

 by a perfect induction without any mixture of hypo- 

 thesis; so if we find, on and beneath the surface of 

 our planet, masses exactly similar to deposits from 

 water, or to results of the cooling of matter melted 

 by fire, we may justly conclude that such has been 

 their origin ; and if the effects, though similar in kind, 

 are on a far larger scale than any which are produced 

 now, we may rationally, and without hypothesis, con- 

 clude that the causes existed formerly with greater 

 intensity. Further than this no geologist of autho- 

 rity has, since the rise of the present enlightened school 

 of geological speculation, attempted to go. 



In many geological inquiries it doubtless happens 

 that although the laws to which the phenomena are 

 ascribed are known laws, and the agents known 

 agents, those agents are not known to have been pre- 

 sent in the particular case. Thus in the speculation 

 respecting the igneous origin of trap or granite, the 

 fact does not admit of direct proof, that those sub- 

 stances have been actually subjected to intense heat. 

 But the same thing might be said of all judicial inqui- 

 ries which proceed upon circumstantial evidence. 

 We can conclude that a man was murdered, although 

 it is not proved by the testimony of eye-witnesses 

 that a man who had the intention of murdering him 

 was present on the spot. It is enough if no other 

 known cause could have generated the effects shown 

 to have been produced. And so, in geology, it is 

 enough that no other known agent than heat could, 

 according to any known law, have produced the 



