196 THE CARBONIFEROUS SYSTEM. 



apparent anomalies were, however, wise contrivances to fit the plant 

 for its office in nature. 



One peculiarity in these heds well illustrates the fact already 

 mentioned, that the thickness of beds is no certain criterion of the 

 time occupied in their formation. The bed of sandstone, eight feet in 

 thickness, enveloping the Calamites, must have been deposited in a 

 few years at most. The underlying coal is all that marks the growth, 

 submergence, and decay of a forest. 



Subdivision XXIII. is a great and continuous series of swamp and 

 estuary deposits, including the most important bed of coal in the 

 section, and a large number of well-marked terrestrial surfaces. It 

 commences with a black bituminous underclay, a soil probably of long 

 continuance, and filled with rootlets. This supports a foot of coal 

 known to the miners as the " Queen's Vein " (Coal-group 8), above 

 which we find three other coals with underclays, and one of them 

 with a shale roof full of prostrate plants. Then we have an underclay 

 capped by shale with fossil leaves, but no coal. Above this we have 

 an interruption of the previous conditions, by the deposition of sand, 

 on the surfaces of which drift-plants were scattered, and became 

 tenanted by the little worms whose shells we have referred to Spirorbis. 

 On these sandstones Stigmaria again took root, and one bed is filled, 

 from the cliff to low-water mark, with well-preserved stools of these 

 singular roots, each with four main divisions, branching dichotomously. 

 A single inch of impure coal was the result of this dense growth of 

 trees. Above this accumulated a thick boggy underclay, on which 

 a varied and beautiful forest has grown, which was overturned or 

 uprooted, and now lies prostrate in a thin band of ironstone and shale. 

 In the ironstone of this band are four species of Sigillaria, and great 

 multitudes of Cordaites and other leaves. All these fossils had 

 Spirorbis attached. They no doubt mark the site of a submerged and 

 fallen forest, which but for the abundant deposition of fine mud and 

 carbonate of iron, which followed its submergence after an interval 

 sufficiently long for the growth of Sjnrorbis, would have appeared as 

 a thin coaly layer. Above this, after an interval occupied by shales 

 and sandstone with one thin coal, we find a thin coaly layer almost 

 entirely composed of Cordaites. No roots appear in the underlying 

 shale, and we may therefore doubt whether these leaves grew in situ, 

 or were scattered over the bottom of water. On this coal is a thick 

 clay supporting, some years ago, two erect stumps. From the clay in 

 which they were rooted they passed upward, through a sandstone two 

 feet in thickness, into a shale with ironstone bands above. The 

 smaller stump was fluted, but without leaf-scars. Its roots were 



