THE FORMATION" OF COAL. 139 



We have first the under-clay due to the beginning of this 

 state of things, during which the hill slopes were slowly 

 acquiring the first germs of subsequent forest life, and were 

 nursing them in their scanty youth. This deposit would be a 

 mineral mud with a few fossils and that fragmentary or fine 

 deposit of vegetable matter that darkens the carboniferous 

 shales and stripes the sandstones. Such a bed of dark con- 

 solidated mud, or fine clay, is found under every seam of coal, 

 and constitutes the " floor" of the coal-pit. The characteristic 

 striped rocks the " linstey" or " linsey" of the Welsh colliers 

 is just such as I found in the course of formation in the 

 Aachensee near the shore, as described above. 



The prevalence of estuarine and lacustrine fossils in the Coal 

 Measures is also in accordance with this : the constitution of 

 coal-ash is perfectly so. Its extreme softness and fineness of 

 structure ; its chemical resemblance to the rocks around, and 

 above, and below ; the oblong basin form common to our coal- 

 seams ; the apparent contradiction of such total destruction of 

 vegetable structure common to the true coal-seams, while 

 immediately above and below them are delicate structures well 

 preserved, is explained by the more rapid deposition of the 

 latter, and the slow soddening of the former as above 

 described. 



I do not, however, offer this as an explanation of the forma- 

 tion of every kind of coal. On the contrary, I am satisfied that 

 cannel coal, and the black shales usually associated with it, 

 have a different origin from that of the ordinary varieties of 

 bituminous coal. The fact that the products of distillation of 

 cannel and these shales form different series of hydrocarbons 

 from those of common coal, and that they are nearly identical 

 with those obtained by the distillation of peat, is suggestive of 

 origin in peat-bogs, or something analogous to them. 



To the above I may add the concluding sentences of the 

 chapter on Coal in Ly ell's ** Elements of Geology." Speaking 

 of fossils in the Coal Measures, he says : " The rarity of air- 

 breathers is a very remarkable fact^when we reflect that our 

 opportunities of examining strata in close connection with ancient 

 land exceed in this case all that we enjoy in regard to any 

 other formations, whether primary,. secondary, or tertiary. We 

 have ransacked hundreds of soils replete with the fossil roots 

 of trees have dug out hundreds of erect trunks and stumps 

 which stood in the position in which they grew, have broken 

 up myriads of cubic feet of fuel still retaining its vegetable 



