OF CREATION. 51 



increasing abundance of these animals marks the com- 

 mencement of a new period. 



It is interesting to contemplate the probable con- 

 ditions of the earth's surface and its physical features, 

 as made known to us by these fossil remains ; but in 

 doing so, we ought to bear in mind constantly the 

 true nature and value of the evidence. So far as it 

 is positive so far as we have only to make out the 

 meaning of what we see this is not difficult or 

 doubtful ; but when we begin to draw general con- 

 clusions, and speak of the absence of whole groups, 

 because we do not discover any indications of their 

 existence, we are reasoning from our own view of 

 what, in all probability, and according to analogy, 

 occurred, and not from positive data. Still, as the 

 circle of our knowledge expands, and these conclu- 

 sions, being tried by the test of experience, are found 

 still correct, they do assume more and more the cha- 

 racter of true generalisations, and become at length 

 admitted as truths. I have here, and elsewhere in 

 these pages, endeavoured to give fairly the result of 

 all the evidence at present obtained on the subject, 

 and have usually intimated the existence of a doubt 

 where the amount of evidence seemed to me insuffi- 

 cient. 



