XIV.] LIVING MATTER AND ITS EFFECTS. 245 



manufacture of ordinary illuminating gas. That part of 

 the coal which contributes to the blaze of a fire is removed, 

 while the coke-like portion is left behind. 



The chemical changes which have taken place during the 

 conversion of vegetable matter into the several varieties of 

 coal may be seen by a comparison of their analyses, as 

 given in the following table : — 



Wood (Oak) 



Peat (Irish) 



Lignite (Bovey Tracey) . 

 Bituminous Coal (Nev/castle) 

 Steam Coal (South Wales) . 

 Anthracite (South Wales) 



Changes of the kind indicated by these analyses have 

 been carried on, during the past history of the earth, on an 

 enormous scale ; and the great extent and thickness of the 

 deposits of coal, which have thus been produced, show 

 that vegetable life has played no insignificant part in the 

 formation of the rock- masses which build up the earth's 

 crust. 



^ The quantity of nitrogen being small is added to the oxygen. The 

 analyses are calculated exclusively of the ash, or mineral matter con- 

 tained in the coals. 



^ Exclusive of nitrogen. 



