5# ERA OF THE CARBONIFEROUS FORMATION. 



would gather in every sea, near the mouths of great rivem 

 On the exhaustion of the superabundance of carbonic acid 

 gas, the coal formation would cease, and the earth might 

 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 sys- 

 tem 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 corresponding ends of 

 neighboring fragments. These are held to be results of 

 volcanic movements below, the operation of which is fur- 

 ther seen in numerous upbursts and intrusions of volcanic 

 rock, (trap.) That these disturbances took place about 

 the close of the formation, and not later, is shown in the 

 fact of the next higher group of strata being comparative 

 ly undisturbed. Other symptoms of this time of violence 

 are seen in the beds of conglomerate which occur amongst 

 the first strata above the coal. These, as usual, consist 

 of fragments of the elder rock, more or less worn from 

 being tumbled about in agitated water, and laid down in 

 a mud paste, afterwards hardened. Volcanic disturban- 

 ces break up the rocks ; the pieces are worn in seas ; and 

 a deposit of conglomerate is the consequence. Of por- 

 phyry, there are some such pieces in the conglomerate of 

 Devonshire, three or four tons in weight. It is to be ad- 

 mitted for strict truth, that, in some parts of Europe, the 

 carboniferous formation is followed by superior deposits, 

 without the appearanoe of such disturbances between 

 their respective periods ; but apparently this case belongs 

 to the class of exceptions already noticed.* That disturb- 

 ance was general, is supported by the further and impor- 

 tant fact of the destruction of many forms of organic being 

 previously flourishing, particularly of the vegetable king- 

 dom. 



* " Some of the most considerable dislocations of the border of the 

 coal fields of Coalbrookdale and Dudley, happened after the depo- 

 sition of a part of the new red sandstone ; but it is certain that those 

 of Somersetshire and Gloucestershire were completed before the 

 date of that rock." — Philips 



