148 ON THE FORMATION OF COAL v 



commonly known as " submarine forests " are to 

 be seen at low water. They consist, for the most 

 part, of short stools of oak, beech, a,nd fir-trees, 

 still fixed by their long roots in the bed of blue 

 clay in which they originally grew. If one of 

 these submarine forest beds should be gradually 

 depressed and covered up by new deposits, it 

 would present just the same characters as an 

 under-clay of the coal, if the Sigillaria and 

 Lcpidodcndron of the ancient world were sub- 

 stituted for the oak, or the beech, of our own 

 times. 



In a tropical forest, at the present day, the 

 trunks of fallen trees, and the stools of such trees 

 as may have been broken by the violence of 

 storms, remain entire for but a short time. Con- 

 trary to what might be expected, the dense wood 

 of the tree decays, and suffers from the ravages of 

 insects, more swiftly than the bark. And the 

 traveller, setting his foot on a prostrate trunk, 

 finds that it is a mere shell, which breaks under 

 his weight, and lands his foot amidst the insects, 

 or the reptiles, which have sought food or refuge 

 within. 



The trees of the coal forests present parallel 

 conditions. When the fallen trunks which have 

 entered into the composition of the bed of coal 

 are identifiable, they are mere double shells of 

 bark, flattened together in consequence of the 

 destruction of the woody core ; and Sir Charles 



