516 PALfflONTOLOGICAL REPORT OF GEOLOGICAL SURVEY. 



or shells, must give the most reliable character for the identification of 

 the beds of coal. 



There is no doubt, but after the formation of each bed of coal all the 

 plants, and the animals belonging to it, have been destroyed, or at 

 least removed far away. The vegetation of the marshes has been cov- 

 ered by thick bed of shales; the shales themselves, with their own in- 

 habitants, have been again covered either by marine deposits of lime- 

 stone, showing the remains of other peculiar species of organized be- 

 ings, or by sandstone swept in by the high sea, and entirely destitute 

 of animal remains. But even, when a bed of coal has again been 

 formed over the marine shales, without any intermediate stratum, the 

 formation of the fire-clay and the vegetation of the coal, both entirely 

 barren of marine animals, both indicate a condition of things and a 

 lapse of time which would, in all probability, have destroyed even 

 their germs. If then, after the formation of a new bed of coal, and 

 after an immense number of years, the downward movement of the 

 surface brings again over it, the marine water and its inhabitants, is it 

 rational to expect that this water will be still charged with the same 

 species of animals as before, and that those animals will be distributed 

 in the same proportion? Is it even rational to suppose, that all the cir- 

 cumstances producing the overflowing will be the same, with the same 

 proportion in the quantity of marine water, the same chemical ele- 

 ments, the same depth, the same temperature, &c, &c. If there is on- 

 ly a small change of the elements dissolved in the water, (and truly, 

 all the shales at different levels present different appearances,) it is cer- 

 tain that this change ought to have influenced the life, viz: the distri- 

 bution of animals in the shales. 



It is even so with the plants. The surface of a marsh having been 

 overflowed, and its vegetation destroyed, we cannot but admit that if it 

 begins again in a new sheet of water, arid after a number of centuries, 

 the distribution of this new vegetation will be somewhat different from 

 the former. If there are no new species of plants, and certainly 

 there ought to be some, at least some of the former p lants have 

 entirely disappeared and those which have been left are grouped 

 in another proportion. Nature bears in one hand its scythe 

 of death, and in the other its cup of life. At every geological change 

 that closes the career of some living species, there appear some others, 

 that were prepared for existence and begin their mission. And although 



