THE FORMATION OF COAL. 91 



All these and other difficulties that have stood so long 

 in the way of a satisfactory explanation of the origin of 

 coal appear to me to be removed if we suppose that during 

 the Carboniferous Period Britain and other coal-bearing 

 countries had a configuration similar to that which now 

 exists in Norway, viz., inland valleys terminating in marine 

 estuaries, together which inland lake basins. If to this we 

 superadd the warm and humid climate usually attributed 

 to the Carboniferous Period, on the testimony of its vege- 

 table fossils, all the conditions requisite for producing 

 the characteristic deposits of the Coal Measures are ful- 

 filled. 



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 carbo- 

 niferous shales and strips the sandstones. Such a bed of 

 dark consolidated 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 constitu- 

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

 fineness of structure; its chemical resemblance to the rocks 

 around, and above, and below; and oblong basin form com- 

 mon 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 for- 

 mation of every kind of coal. On the contrary, I am satis- 

 fied that cannel coal, and the black shales usually associated 

 with it, have a different origin from that of the ordinary 



