284 



measures, where 120 beds are superposed on one another, 

 exclusive of a great many which are less than a foot in thick, 

 ness ; the coal beds at Johnstone, in Scotland, and those in the 

 Creuzot, in Burgundy, are some of them, respectively, thirty 

 and fifty feet in thickness,* whilst in the forests of our tempe- 

 rate zones the carbon contained in the trees, growing over a 

 certain area, would hardly suffice, in the space of a hundred 

 years, to cover it with more than a stratum of seven French 

 lines in thickness. f Near the mouth of the Mississippi, and 

 in the " wood hills" of the Siberian Polar Sea, described by 

 Admiral Wrangel, the vast number of trunks of trees accu- 

 mulated by river and sea-water currents, affords a striking 

 instance of the enormous quantities of drift wood which must 

 have favoured the formation of carboniferous depositions in 

 the inland waters and insular bays. There can be no doubt 

 that these beds owe a considerable portion of the substances 

 of which they consist to grasses, small branching shrubs, and 

 cryptogamic plants. 



The association of palms and conifcree which we have indi- 

 cated as being characteristic of the coal formations, is dis- 

 coverable throughout almost all formations to the tertiary 



black coal. The coal and the unaltered amber lay side by side. Regard- 

 ing the part which the lower forms of vegetation may have had in the 

 formation of coal-beds, see Link, in the Abhandl. der Berliner Akade- 

 mie der Wissenscliaften, 1838, s. 38. 



* [The actual total thickness of the different beds in England varies 

 considerably in different districts, but appears to amount in the Lanca- 

 shire coal-field to as much as 150 feet. Ansted's Ancient World, p. 78. 

 For an enumeration of the thickness of coal measures in America and 

 the Old Continent, see Mantell's Wonders of Geology, vol. ii. p. 69.] 

 Tr. 



t See the accurate labours of Chevandier, in the Comptes rendus df 

 FAcaddmie des Sciences, 1844, t. xviii. pt. i. p. 285. In comparing this 

 bed of carbon, seven lines in thickness, with beds of coal, we must not 

 omit to consider the enormous pressure to which the latter have been 

 subjected from superimposed rock, and which manifests itself in the 

 flattened form of the stems of the trees found in these subterranean 

 regions. " The so-called wood-hills discovered in 1806 by Sirowatskoi, 

 on the s nith coast of the Island of New Siberia, consist, according to 

 Hedenstrom, of horizontal strata of sandstone, alternating with bitu- 

 minous trunks of trees, forming a mound thirty fathoms in height ; at 

 the summit the stems were in a vertical position. The bed of drift- 

 wood is visible at five worsts distance." See Wrangel, Reise Icings dvr 

 Nvrdlcuste von Siberian in den Jahren 1820-24, th. i. s. 102, 



