550 THE UNIVERSE. 



plants which produced the antediluvian combustible, and 

 from these primitive medals of creation we have seen 

 science weave the history of the dawn of terrestrial veg- 

 etation. 



But by what mysterious phenomena was this extraor- 

 dinary transformation effected ? At first it was thought 

 that the forests of the coal era had been overthrown or 

 borne away by the violence of currents, and that their 

 trunks, locked together after having floated about like im- 

 mense rafts, had collected in creeks, and there become 

 changed into layers of coal. 



But this theory, though seductive from its simplicity, is 

 inadmissible, because the trunks, in spite of their bulk, 

 would yield only a very thin layer of coal. M. Elie de 

 Beaumont, on the other hand, thinks that it was the com- 

 pact, herbaceous vegetation enveloping the great plants of 

 the coal-forests which played the principal part in the pro- 

 duction of coal, and that by its ceaseless renewal and change 

 the coal was produced by a transformation analogous to that 

 which our aquatic plants undergo when transformed into 

 turf. This theory offers a better explanation of the abun- 

 dance and thickness of the coal-seams. We do not exactly 

 make out the nature of the chemical phenomena which 

 must have taken place during such a fundamental meta- 

 morphosis ; but what is clear is that this was principally 

 effected under the influence of the immense pressure and 

 great heat which the plants experienced during the time 

 they were submerged under water, owing to the subsidence 

 of the soil on which they had lived and died. 



