PAL^EONTOLOGICAL REPORT OF GEOLOGICAL SURVEY. 533 



roots or, as I think, were creeping rootstocks, producing trees under 

 favorable circumstances, their presence in a bed of coal, where they 

 could not creep, as in the water, and where their direction was neces- 

 sarily changed by many circumstances, indicates that there were plen- 

 ty of trees living at the time of the formation of this coal. If the trees 

 had had the same hardened silicious bark as the Stigmaria, their out- 

 line would also have been preserved; but being especially of conifer- 

 ous or resinous species, they have been entirely transfoi med into coal. 

 This shows that the cannel coal results from the abundance of some 

 kinds of trees, especially Sigillaria and Lepidodendron, or perhaps Lepi- 

 dodendron only. Moreover, the chemical composition of some plants, 

 especially of roots, depends on the place where they grow; on the wa- 

 ter which they absorb. The needles or leaves of coniferous trees, for 

 example, living on the limestone, contain only two per cent, of silica, 

 when the same species, living on silicious ground, have as much as five 

 to six per cent, of it. We must therefore suppose, that according to 

 their habitation, the Stigmaria would necessarily show a difference in 

 their composition. 



The analysis of the Breckinridge coal proves, nevertheless, that 

 though it has been formed of resinous trees, since it contains sixty- 

 three per cent, of volatile matter, there were abundantly mixed with it 

 plants highly charged with siliceous matter — the Stigmaria certainly — 

 for it gives by combustion as much as eight per cent, of ashes. 'I he 

 main coal of the Shawneetown Company, at quite a different level, is 

 also very bituminous, doea not show any trace of Stigmaria, and has 

 only one half per cent, of ashes. 



If it had been possible to see at once, and opened, all the beds of 

 the Coal Measures in successive order, the true characteristic fossils of 

 every one of them could perhaps have been examined and described; 

 but in a level country, where the highest hills do not exceed three hun- 

 dred feet, suck an examination is no where possible. In both places 

 where, accordiug to your directions, we could expect to see a succession 

 of coal beds, at different levels, viz; at Shawneetown, and at the Saline 

 Mining Company's works, in Illinois, we had good opportunities to 

 study the fossils of vein Nos, 9, and 11. ,At the Kentucky Coal Com- 

 pany mines, we saw open one bed still lower— No. 6, or Little vein. But 

 we.did not find any place where beds 2, 3, 4, 5, 7, and 8, were opened. 



