ON THE ORIGIN OF COAL. 1G7 



The outsides of both stones are well coated 

 with a covering of Coal, showing that they 

 must have lain long in the places where they 

 were found. 



As previously remarked, dry land has been 

 inferred to exist, during the formation of the car- 

 boniferous series, from the characters of the 

 fossil plants discovered embedded in it. The 

 true nature of these plants, however, is at present 

 but little understood, and calculated to puzzle 

 the most eminent recent botanists, rather than 

 throw much light upon the soil upon which they 

 grew. Wherever the plants grew, the strata, in 

 which they are found, were no doubt deposited 

 from water, and show no evidence of having been 

 dry land. Had dry land existed during that 

 period, some evidence of it would, in all proba- 

 bility, have been left during the deposition of the 

 flags of the lower Coal-field, as we there find thin 

 beds of fine sandstone, alternating with thin 

 deposits of silty clay. The latter of which, 

 — if exposed to the action of the sun or air 

 for a few hours, even so short a time as the 

 reflux of the tidal wave of our present seas — 

 would have left some evidence of desiccation, 

 and consequent contraction. 



