in the Neighbourhood of Edinburgh. 253 



been transported into the basins which they have occupied, by 

 the sudden or gradual operation of streams or rivers. Some sand- 

 stones, as, for instance, certain beds to the east of Dunbar, contain 

 marine shells, while the majority of other sandstones inclose nu- 

 merous plants, and thus afford indications rather of lacustrine 

 than of marine deposits. 



Argillaceous shale, which, in the limestone quarries of Gilmer- 

 ton, is filled with marine shells, and at Burdiehouse contains the 

 freshwater unio, represents the mud, or silt, accumulated in the 

 beds of ancient rivers, fresh- water lakes, or seas. 



Limestones, as I have urged, may be of two kinds. While 

 that of Gilmerton, adjacent to the Burdiehouse quarry, abounds 

 in corallines, encrinites, and shells, all evidently marine, these are 

 in vain sought for in the other limestone which presents the re- 

 mains of fish, apparently inhabiting fresh- water, and of ferns, ly- 

 copodiaceous plants, and such aquatic vegetables as flourish most 

 among fresh- water lakes and marshes. While the one limestone, 

 therefore, is the memorial of a sea, the other limestone indicates . 

 some fresh-water river or lake, within which calcareous matter 

 was elaborated. 



With regard to coal, most of the seams of this substance have 

 resulted from the decay of vegetables which have grown upon the 

 very site in which such seams of coal are found. This fact has 

 been incontestibly shewn in the Northumberland coal-field, where 

 the large roots of Stigmariag have been traced in coal or shale, in- 

 dicative of the vegetable mud in which they grew. It has been 

 therefore inferred, that many of the plants of coal-fields flourish- 

 ed in still and shallow water. — (See Preface to Vol. JL of the 

 Fossil Flora of Professor Lindley and Mr Hut ton.) Some 

 species of coal, however, it is supposed, might have been brought 

 from a distance in the form of drifted vegetable matter, to which 

 origin certain kinds of cannel, or parrot-coal, are referred. But 

 the absence of all attrited, or water- worn pebbles within the sub- 

 stance of coal, is fatal to this alleged origin. 



