184 



THE GEOLOGIST, 



perties. In fact most of the facts in natural history can be explained 

 by this theory ; but there are a few which at present cannot, such as 

 the colours of certain larvae, which are asexual. Even these may 

 perhaps be the effects of the mysterious and unknown laws of corre- 

 lation of growth and sympathy between different parts. 



We must remember that the theory of natural selection is subordi- 

 nate to, and totally distinct from, that of the transmutation of species; 

 and that if the former should be found wanting it would not effect the 

 latter in the least degree. 



The third great argument urged against the theory of transmutation 

 of species is the geological one ; and may be divided into two heads. 



1. The almost entire absence* of the remains of the numerous con- 



necting links that must have existed . 



2. The sudden appearance of groups of allied species, particularly 



in the lowest known fossiliferous formations. 



The answer to the first is that the geological record is extremely 

 imperfect. There are reasons for thinking that most sedimentary 

 strata have been formed during subsidence. Besides the difficulty of 

 accounting for the very thick ones in any other way, we must re- 

 member that during subsidence a newly-formed deposit has the 

 advantage of remaining quiet until it has had time either to harden 

 or to be covered up. When land is rising, on the contrary, the loose 

 deposits will be continually washed further and further away from it 

 until a period of rest or subsidence gives them time to consolidate ; 

 but while subsidence is going on the land and the inhabitable part of 

 the sea will be decreasing, consequently there will be much extinction 

 and little variation. When land is being elevated the contrary will 

 obtain, therefore, most of the intermediate varieties will not be 

 preserved. 



Most sandstones and clays have been accumulated near land ; for 

 the finest mud or sand must sink before it can travel very far. Even 

 in the exceptional case of the mouth of a great river, sediment 

 has never been detected more than three hundred miles from the 

 land. If rolled along the bottom by a current it would be stopped 

 by the first valley it came across, which would act as a purifier to the 

 current in the same way that a lake does to a river. Limestones may 

 certainly be formed at any depth ; but we have proofs in the organic 

 remains of which they are generally full that most of them were 

 deposited in not very deep water ; and although some, like chalk, may 

 be forming in the middle of the ocean, yet I think that the purity of 

 deep water in most places, as proved by its blue colour,t is a sufficient 

 guarantee that no deposition is going on ; and that this is true is 



* One reviewer has even said the " thorough and complete absence." See An . 

 Nat. Hist, Feb. I860, p. 140. 



* It is the purity, not the depth of the blue that proves the absence of 

 sediment j the depth of colour depends in a great measure on the quantity of salt 

 it contains in solution. The North Atlantic between Ireland and Canada is not 

 pure blue. 



