420 ON THE GEOLOGICAL RELATIONS 



while the causes of a scanty evidence of this kind are 

 obvious. We may allow that the living animals were 

 less numerous and abundant at the earlier periods; 

 and the rarity of primary limestone is a sufficient proof 

 of this ; but that is all. And if also the whole of the 

 primary series was formed beneath the water at one 

 period of repose, as appears true from the parallelism 

 of the strata, it would be an extraordinary conclusion 

 that a creation should have occurred late in that pe- 

 riod, and not at its commencement, as has been the 

 case apparently in all the successive ones. 



In the secondary series, organic bodies are rare in 

 the lowest sandstone. And this is intelligible, because, 

 at so early a date after a great revolution, they could 

 not have abounded in the ocean ; while it is probable 

 also that much of this deposit consists of antient ter- 

 restrial alluvia, produced in a manner I shall hereafter 

 explain. Hitherto, with the probable exception 

 of Anthracite, every fossil is marine ; and this 

 continues through the next, or mountain limestone, 

 where they become abundant ; because, like all other 

 secondary limestones, it has been formed from their 

 remains, as it could not indeed have been produced 

 from any other source. But here the exclusion ter- 

 minates, and here also commence terrestrial vegetables 

 as well as animals. Whether they existed as living 

 ones before this, we do not know; and, again, ought 

 not to decide that they did not, from negative evidence. 



The coal strata are here the great depository of 

 terrestrial organic fossils; of plants and fresh- water 

 shells : and I need not distinguish these strata further, 

 than to say that the fossils occur chiefly in the shales, 

 and in the limestones, when any are present; as ve- 

 getable fragments in the shape of charcoal are found 

 in the coal itself. In the rnagnesian limestone, they 



