10 REMARKS ON THE VEGETABLE REMAINS 



even of these beds, with their accompanying shales, possess them sparing- 

 ly, and some not at all. 



If, therefore, we only find these impressions of vascular cryptogamic 

 plants partially distributed, what particular reason have we for maintaining 

 the almost exclusive production of coal from ferns, equisetaceae, and other 

 plants of that family, when we find so many phanerogamic plants abound- 

 ing in these early sedimentary deposits ? 



If from various specimens of jet and Bovey coal, which are in the pos- 

 session of many of my friends and in my own, no doubt can be entertained 

 that they were originally stems of plants, possessing a ligneous structure, 

 the concentric rings and fibrous tissue being sufficient evidence to the 

 naked eye that such was the case ; and if notwithstanding, from un- 

 known causes, cut them as thin as you like, no true structure can be fairly- 

 traced in them ; are we on that account warranted to doubt their being 

 dicotyledonous or coniferous, or of a structure allied to the latter ? 



If, then, many coals, as well as fossil plants from the mountain lime- 

 stone groups, and true coal-fields, on being cut into thin slices, present a 

 similar appearance, where is the impropriety in assuming the belief that 

 these combustible beds were masses of vascular and cellular cryptoga- 

 mic plants, mixed with gymnospermous phanerogamic trees, or others of a 

 closely allied structure ? 



Except in a few instances, I have ineffectually tried, with the aid of 

 the microscope, to obtain some insight into the structure of coal. Owing 

 to its great opacity, which is probably due to mechanical pressure, the 

 action of chemical affinity, and the percolation of acidulous waters, all 

 traces of organization appear to have been obliterated. After frequent 

 trials, however, I have at length been gratified by the discovery of a regular 

 and beautiful texture in the centre of a piece of coal from the mountain 

 limestone group. This in many respects indicates woody tissue, and un- 

 doubtedly leaves scope for our most sanguine expectations. By the ap- 

 pearance presented by many varieties of coal, particularly that of Berwick- 

 on-Tweed, and that of the Scotch basins, after having been subjected to 

 a certain degree of heat, when it splits and separates in layers almost of 



