/ * PICTURESQUE SKETCHES 



fossils, indicating not only the presence of land, but 

 the existence of a luxuriant and quasi tropical vege- 

 tation, permitting the accumulation of thick and wide- 

 ly-spread beds of coal, which occupy basin-shaped de- 

 pressions in the limestones and sandstones, and which, 

 although more especially abundant in the central 

 parts of North America and in our own island, are 

 recognized also in eastern Europe, on the Donetz ; in 

 various parts of Asia ; and in eastern Australia and 

 Van Diemen's Land. 



It must not be supposed, however, that any con- 

 siderable proportion of the rocks of this, which is 

 generally known as the carboniferous, or coal-bearing 

 period, is actually made up of the remains of vegetable 

 matter. The first of the series of strata thus de- 

 posited seems to have been, in most parts of the world, 

 a solid compact limestone, almost the whole of which 

 is sometimes the result of the labours of the coral 

 insect; and although there are also beds of limestone 

 in the more ancient part of the first great series 

 evidently formed by these little animals, yet these 

 bear no proportion whatever, either in extent of sur- 

 face or in thickness, to the coralline limestones of 

 the newer period we are about to describe. In the 

 British Islands it would appear that the most con- 

 siderable masses of limestone were formed immedi- 

 ately after the deposit of the old red sandstone and 

 devonian rocks had been completed; but we have 

 distinct evidence in the gradual diminution in the size 

 of the pebbles, and at length the alternation of lime- 

 stone with fine marine gravel, that there was neither 

 a sudden change nor a break in the continuity of 

 depositions. It is probable, therefore, that, at the 



