v.] ON THE FORMATION OF COAL. 101 



hollow stools of coal trees of Nova Scotia, the remains 

 of snails, millipedes, and salamander-like creatures, em 

 bedded in a deposit of a different character from that 

 which surrounded the exterior of the trees. Thus, in en 

 deavouring to comprehend 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 and 

 sseds ; 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, carried by the wind 

 to unoccupied regions, extended 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 the reason of the 

 predominance of the spores and spore-cases in it ? 



A ready answer to this question is afforded by the 

 study of a living full-grown club-moss. Shake it upon 

 a piece of paper, and it emits a cloud of fine dust, which 

 falls over the paper, and is the well-known Lycopodium 

 powder. Now this powder used to be, and I believe 

 still is, employed for two objects, which seem at first 

 sight to have no particular connection with one another. 

 It is, or was, employed in making lightning, and in 

 making pills. The coats of the spores contain so much 



