NATURAL I 11 STORY OF CREATION. 75 



again become a suitable theatre of being for land 

 animals. 



The termination of the carboniferous formation is 

 marked by symptoms of volcanic violence, which some 

 geologists have considered to denote the close of one 

 system of things and the beginning of another. Coal 

 beds generally lie in basins, as if following the curve of 

 the bottom of seas. But there is no such basin which is 

 not broken up into pieces, some of which have been 

 tossed up on edge, others allowed to sink, causing the 

 ends of strata to be in some instances many yards, and 

 in a few several hundred feet, removed from the corre- 

 sponding ends of neighbouring fragments. These are 

 held to be results of volcanic movements bolow, the 

 operation of which is further seen in numerous upbursts 

 and intrusions of volcanic rock (trap). That these dis- 

 turbances took place about the close of the formation, 

 and not later, is shown in the fact of the next higher 

 group of strata being comparatively undisturbed. Other 

 symptoms of this time of violence are seen in the beds 

 of conglomerate which occur amongst the iirst strata 

 above the coal. These, as usual, consist of fragments of 

 the elder rocks, more or less worn from being tumbled 

 about in agitated water, and laid down in a mud paste, 

 afterwards hardened. Volcanic disturbances break up 

 the rocks ; the pieces are worn in seas ; and a deposit of 

 conglomerate is the consequence. Of porphyry, there 

 are some such pieces in the conglomerate of Devonshire, 

 three or four tons in weight. It is to be admitted for 

 strict truth that, in some parts of Europe, the carbon- 

 iferous formation is followed by superior deposits, with- 

 out the appearance of such disturbances between their 

 respective periods ; but apparently this case belongs to 



