162 ON THE ORIGIN OF COAL. 



of water necessary to drift forests of timber from 

 neighbouring lands, but have every appearance 

 of a hardened mud brought by sluggish water, 

 with scarcely any current. 



The presence of the remains of bivalve shells, 

 and fishes, in cannel, clearly prove that it was 

 formed under water ; but in the Lancashire coal 

 seams we have, as yet, found no remains either 

 of fishes or shells, although there are frequently 

 found in them regular partings of fine silt and 

 fire clay, evidently deposited from water, full of 

 Stigmaria rootlets, and, like the true floors. A thin 

 layer of an inch of unctuous clay generally inter- 

 venes between the bed of Coal and its floor. But 

 there is not any admixture of sand or clay in the 

 Coal itself, to shew that it was drifted, into the 

 places where it is now found, by currents of water. 

 Nearly all the Coal seams, more or less, display 

 evidence of common Coal plants, especially Stig- 

 maria, Sigillaria, and Lepidodendra, pulverulent 

 carbonaceous matter, like charcoal, or shew woody 

 structure under the microscope. 



On the other hand, the roofs or strata imme- 

 diately above the seams of Coal nearly always 

 present some evidence of currents of water. 



