GENERAL INFERENCES. 91 



tralia, from Vancouver's Island in the far west, to the remotest 

 corners of Russia, in Eastern A sia, are possessed of one uniform 

 botanical character, the same species being found in every lati- 

 tude, all now allied to those only of tropical countries, and 

 when the denseness and luxuriance of an Indian jungle pre- 

 vailed in every clime. 



A calculation has actually been made of the amount of woody 

 substance contained in a given quantity of coal.* The results, 

 which are highly interesting, are as follow : wood affords in 

 general about twenty per cent., and coal about seventy per 

 cent, of charcoal. Throwing out of the calculation the oxygen 

 and hydrogen, it must therefore have required three and a half 

 tons of wood to produce the charcoal contained in one ton of 

 coal. Suppose now a forest, composed of trees, every one of 

 which is eighty feet high — that the trunk of each tree contains 

 eighty cubic feet, and the branches forty — and it results, that 

 the weight of each will be about two and a quarter tons. Allow- 

 ing one hundred and thirty such trees to an acre, we have three 

 hundred tons of woody matter on that area of ground. Now a 

 cubic yard of coal weighs very nearly one ton ; a bed of coal 

 one acre in extent, and three feet thick, will contain about four 

 thousand eight hundred tons ; and hence one acre of coal, with 

 only one bed of three feet thick, is equal to the produce of nearly 

 two thousand acres of forest. But instead of one bed there is 

 an average of eight to ten in the coal-measures of Scotland, 

 with an average aggregate thickness of twelve feet of the pure 

 mineral substance ; in England, there is a much higher ratio ; 

 and in the vast coal basins of America it is higher still. We 

 leave the reader to pursue for himself the arithmetical enume- 

 ration and comparison which these data furnish ; and we may 

 simply ask him to consider what amount of forest, all the world 

 over, is now buried in these subterranean regions, shedding, 

 year after year, their leaves and fruits to fill up the dense bitu- 

 minous mass, and where the lands on which their mighty trunks 



* Geology of Fife and the Lothians, p. 116, b}' C. Maclaren, Esq., F.R.S.E. 



