§ 8. GREAT DISMAL SWAMP. 67 I 



a soft black mud, without any traces of organization. Numerous 

 trunks of large and tall trees lie buried in the black mire of the 

 morass. In the midst of the swamp there is a lake of an oval form, 

 seven miles long, five wide, and the depth, where greatest, fifteen feet ; 

 its bottom consists of mud like the swamp, but which in some places 

 is covered by a pure white sand, a foot deep. This sheet of water is 

 usually even with the banks, on which a tall and thick forest grows. 



"The phenomena above described help us greatly," observes Mr. 

 Lyell, "to conceive the manner in which the coal of the ancient 

 carboniferous rocks may have been formed. The heat, perhaps, may 

 not have been excessive when the coal-measure originated, but the 

 entire absence of frost, with a warm and damp atmosphere, may have 

 enabled tropical forms to flourish in latitudes far distant from the line. 

 The frequent submergence of masses of vegetable matter like the 

 morass, beneath seas or estuaries, as often as the land sank down 

 during subterranean movements, may have given rise to depositions of 

 strata of mud, sand, or limestone, immediately upon the vegetable 

 matter. The conversion of successive surfaces into dry land, on which 

 other swamps supporting trees were formed, might give origin to a 

 continued series of coal measures, of great thickness."* 



The above is a concise exposition of this theory by one of 

 its ablest advocates, and is therefore deserving every con- 

 sideration ; but until it can be shown that pure beds of coal 

 are being formed under such conditions, the hypothesis, 

 however ingenious, appears to me to be without any support 

 from facts. To render the " Great Dismal " a modern 

 example of the mode in which the ancient coal-measures 

 were formed, it is necessary to obtain evidence that beds of 

 coal have been and are still being produced in this morass. 



9. Upright Trees in the Coal Measures. — The 

 occurrence of trees in an upright position, in some instances 

 with their roots attached, and extending into the under-clay, 

 is regarded as another unequivocal proof of the formation of 

 coal from vegetables growing on the spot. Several instances 

 of this kind have been observed in England. One of the 

 most remarkable was brought to light a few years since in 

 forming the Bolton and Manchester railway. Near Dixon- 



* Travels in America, vol. i. chap. vii. 



