204 LAY SERMONS, ADDRESSES, AND REVIEWS. [x. 



(and those not of the first order) would have been 

 induced by mere love of detail, as such, to study the 

 minutiae of osteology, were it not that in such minutiae 

 lie the only keys to the most interesting riddles offered 

 by the extinct animal world. 



These assuredly are great and solid gains. Surely it 

 is matter for no small congratulation that in half a cen- 

 tury (for palaeontology, though it dawned earlier, came 

 into full day only with Cuvier) a subordinate branch of 

 biology should have doubled the value and the interest 

 of the whole group of sciences to which it belongs. 



But this is not all. Allied with geology, palaeon- 

 tology has established two laws of inestimable import- 

 ance : the first, that one and the same area of the earth's 

 surface has been successively occupied by very different 

 kinds of living beings ; the second, that the order of 

 succession established in one locality holds good, approxi- 

 mately, in all. 



The first of these laws is universal and irreversible ; 

 the second is an induction from a vast number of 

 observations, though it may possibly, and even pro- 

 bably, have to admit of exceptions. As a consequence 

 of the second law, it follows that a peculiar relation 

 frequently subsists between series of strata, containing 

 organic remains, in different localities. The series 

 resemble one another, not only in virtue of a general 

 resemblance of the organic remains in the two, but also 

 in virtue of a resemblance in the order and character 

 of the serial succession in each. There is a resemblance 

 of arrangement ; so that the separate terms of each series, 

 as well as the whole series, exhibit a correspondence. 



Succession implies time ; the lower members of a 

 series of sedimentary rocks are certainly older than 

 the upper ; and when the notion of age was once 

 introduced as the equivalent of succession, it was no 



