312 COAL. 



growth of these vegetables in low moist forests, in 

 marshes, or on the borders of lakes or rivers. In the 

 repetition of different strata, we see the successive de- 

 position of earthy matters of different natures, after- 

 wards consolidated into sandstone or shale, or else re- 

 maining unconsolidated ; while the repetition of car- 

 bonaceous beds, no less than the deposition of vege- 

 table strata alternating with the laminae of the shales, 

 shows that successive generations of plants had fol- 

 lowed successive depositions of earth. To the same 

 circumstances of repose, the solution of soluble earths, 

 pressure, and, it is possible, to heat, we must attri- 

 bute equally the consolidation of the rocks and the 

 conversion of the vegetable deposits to coal, as I shall 

 hereafter explain more fully. 



Although the vegetable nature of these remains 

 thus indicates the terrestrial origin of the series, the 

 subjacent limestone contains marine remains. These 

 strata then, as I remarked under former general views, 

 have been formed under the sea, of which the bottom 

 must have been elevated prior to the deposition of the 

 coal beds. That the vegetables could riot have been trans- 

 ported from their places of growth to that position, is 

 no less proved by the integrity of the most delicate 

 'specimens, than by the erect trunks of trees above- 

 mentioned. Yet though assuredly formed on the 

 supramarine land, it may still seem difficult to account 

 for the great thickness of many deposits, and for the 

 frequent alternations of rocks and of vegetable matter. 

 The existence of deep lakes, at some period and under 

 various modifications, is necessary to explain the phe- 

 nomena ; though it may be difficult to conceive the 

 exact details of the changes, and the condition of the 

 surface necessary for their production. In the history 

 of the later lacustral formations there are analogous 



