FORMATION OF COAL. 



seemingly not so in this country, they always occur, but not in 

 masses ; and I have frequently found Stigmaria in the roof of 

 seams with other remains, which is important. Considerable 

 weight has been attached by Dr. Dawson and others, to the Flora 

 found over coal, giving a clue to its origin. 



Now the belief is that the plants which formed coal grew on the 

 spot where the coal now lies, and that the underclay was the soil 

 in which they flourished j then if these plants were the same as 

 those which we now find in a fossil state over the coal, one would 

 expect to find them immediately over: such, however, is not so, 

 with the exception of Cordaites. Erect forests are very rare, a 

 stump e?^ situ is not common, the majority having drifted into their 

 present positions. In many seams of coal, what are termed 

 " coalstones ' ' occur. These are probably hollow trunks or branches 

 of trees, chiefly Lycopodiaceae, which have been filled with debris 

 while in water, and at last, owing to the increased W:^ight, have 

 sunk into the coal-forming vegetation which had been submerged. 

 The idea is suggested by the shape, and specimens have been 

 found which remove all doubt as to their origin, a considerable 

 number being Stigmaria. The envelope surrounding the nucleus 

 of debris is that of epidermis, which resisted decay more than the 

 other parts. 



In other seams what appear to be bands of dirt occur in the coal, 

 from a few inches to four feet long, and from one to three inches 

 thick. These have much the same origin as coalstones, but in this 

 case the hollow stem has not been all filled up, and the weight of 

 the strata deposited over has pressed the cylinder flat, causing the 

 sides to burst. 



These facts appear to show that the Lycopodiaceae, and probably 

 Calamites, resisted decay more than did the coal-forming plants, 

 and that they were placed, where now found, by accident. The 

 vegetable matter (epidermis) in these coalstones has been partially 

 formed into coal, but ought not to be taken for microscopical 

 sections, with a view of gaining a knowledge of the structure of the 



