N<> LH rUBM ON EVOLUTION TTT 



I..- iiu i ..iiijl.-t.-. ili;it it .-an only preserve remains 

 t'. .nnl in certain favourable localities and under 



bicular conditions; that it must be destroyed 



ly process.-* of denudation, and obliterated by 



a of metamorphosis. Beds of rock of any 



'liickness. crammed full of organic remains, may 



cither by the percolation of water through 



'hfin. or by the influence of subterranean heat, 



lose all trace of these remains, and present the 



appearance of beds of rock formed under c<n- 



ns in which living forms were absent. Such 

 metamorphio rocks occur in formations of all a 

 and, in various cases, there are very good grounds 

 I'm- the belief that they have contained organic 

 remains, and that those remains have been abso- 

 lutely obliterated. 



I insist upon the defects of the geological re- 

 cord the more because those who have not 



nded to these matters are apt to say, " J 

 all very well, but, when you get into a difficulty 

 with your theory of evolution, you appeal to the 

 incompleteness and the imperfection of the geo- 

 logical record ; " and I want to make it perfectly 



i r to you that this imperfection is a great fact, 

 which must be taken into account in all our 

 speculations, or we shall constantly be going 

 wrong. 



You see the singular series of footmarks, drawn 

 if its natural size in the large diagram hanging 

 up here (Fig. 2), which I owe to the kindness 



