1 7d On the Formation of Coal, 



The plants found in our coal fields belong to only a few of 

 the great orders of vegetables now existing on ihe ,globe. 

 The most numerous group is the ferns, which also rank lowest 

 in the scale, none of the inferior orders — mosses, lichens, or 

 fungi — having yet been observed. The highest well-ascer- 

 tained group is the ConifersB, or plants bearing cones like our 

 present firs or pines, to which the magnificent fossil stems 

 seen, exposed in Granton and Craigleith quarries, are referred. 

 The class to which tlie Sigillarise, known by the seal-like im- 

 pressions on their stems, belong, is, however, still undecided, 

 some placing them among ferns, others among the Coniferae, 

 others in an intermediate group, and a fourth even higher 

 still among the Euphorbiae or Cacti, natives of the arid de- 

 sert regions of the tropics. These various plants seem to 

 have had a far wider geographical distribution than the simi- 

 lar plants in the present day, showing a uniformity of vege- 

 tation in the northern hemisphere to which no parallel now 

 exists. Even in Melville Island,* deep in the Arctic regions, 

 plants identical with those in the coal formation of Britain 

 are said to have been found, though no explanation has yet 

 been given how plants of such size and so singularly succu- 

 lent and lax in their texture could have flourished in these 

 dreary regions, or endured the continual frosts and the pro- 

 longed withdrawal of the stimulus of light. 



The under-clay or soil on which the coal rests, seldom con- 

 tains any plants except the stigmarige, now considered to 

 be the roots of the sigillarise which permeate its mass, as 

 those of the water-lily and other aquatic plants do the silt 

 at the bottom of still waters. This shows that this clay 

 was either submerged or otherwise unfit for supporting vege- 

 tation. Above this is the coal, formed of the detritus of 

 these plants, and probably of others drifted from other 

 places, though the extreme rarity or entire absence of sand 

 or pebbles in the coal beds is opposed to the idea that much 

 of it can have been brought from a distance by running water. 



* We have specimens of Melville Island coal plants in our possession, and 

 fossils of the same description from Neill's Cliffs in Jameson's Land — a tract 

 of country in a high northern latitude on the east coast of Greenland. — JEdit. 



