V ON THE FORMATION OF COAL 149 



Lyell and Principal Dawson discovered, in the 

 hollow stools of coal trees of Nova Scotia, the 

 remains of snails, millipedes, and salamander-like 

 creatures, embedded in a deposit of a different 

 character from that which surrounded the exterior 

 of the trees. Thus, in endeavouring to compre- 

 hend the formation of a seam of coal, we must try 

 to picture to ourselves a thick forest, formed for 

 the most part of trees like gigantic club-mosses, 

 mares' -tails, and tree-ferns, with here and there 

 some that had more resemblance to our existing 

 yews and fir-trees. We must suppose that, as the 

 seasons rolled by, the plants grew and developed 

 their spores arid seeds ; that they shed these in 

 enormous quantities, which accumulated on the 

 ground beneath ; and that, every now and then, 

 they added a dead frond or leaf; or, at longer 

 intervals, a rotten branch, or a dead trunk, to 

 the mass. 



A certain proportion of the spores and seeds no 

 doubt fulfilled their obvious function, and, car- 

 ried by the wind to unoccupied regions, ex- 

 tended the limits of the forest ; many might be 

 washed away by rain into streams, and be lost ; 

 but a large portion must have remained, to 

 accumulate like beech-mast, or acorns, beneath 

 the trees of a modern forest. 



But, in this case, it may be asked, why does 

 not our English coal consist of stems and leaves 

 to a much greater extent than it does ? What is 



