108 Lord Greenock on the Coal Formation of the 



itself, of the pre-existence of a sufficient extent of dry land, 

 clothed with a luxuriant tropical vegetation, to have supplied 

 this detritus and these remains, and sufficiently elevated to have 

 given rise to the rivers and torrents, by the action of which this 

 transported matter must have been carried down into the lakes 

 or estuaries, in which, to all appearance, such deposits were 

 formed. Whether this land constituted groups of islands, ac- 

 cording to the opinion of many geologists, or continents of great- 

 er or less extent, which, by subsequent revolutions, have been 

 either wholly or partially submerged by the existing sea, is not 

 our present object to inquire ; but, from the size and position of 

 the fossil trees enveloped in many of the beds of this formation, 

 and other phenomena connected with them, there appear to be 

 strong grounds for inferring that the volume of water discharged 

 by these rivers, and the magnitude of their estuaries, must have 

 been much more considerable than would probably have been 

 the case if they had been situated in small islands ; and the oc- 

 currence of terrestrial plants, with the remains of fishes, and of 

 mollusca, that had either been the inhabitants of fresh-water or 

 of shallow seas, in the lowest beds of the series, which have after- 

 wards been covered by other deposits more decidedly of a marine 

 character, seems to shew, that, although the former might have 

 been originally deposited in lakes, or on flat shores near the 

 mouths of rivers, frequent alternations in the relative level of the 

 sea and land may probably have taken place since, by which a 

 corresponding succession of deposits, varying accordingly in the 

 character of their organic remains, have been produced. 



The intermixture, however, of organic remains of a fluviatile 

 character, with those of marine fishes and shells, is very general 

 throughout the coal-measures, and it is still doubtful whether 

 any well-authenticated proof exists of any beds having yet been 

 discovered in the carboniferous series, which, from their organic 

 contents, could be pronounced to have had exclusively a fresh- 

 water origin, unless an exception should be found in the lime- 



