126 THE STORY OF GERM LIFE. 



the carbon is largely prevented, and the vegetable 

 matter slowly changes its character. Under the 

 influence of this slow fermentation, aided, proba- 

 bly by pressure, the mass becomes more and more 

 solid and condensed, its woody character becomes 

 less and less distinct, and there is a gradual loss 

 of the hydrogen and the oxygen. Doubtless 

 there is a loss of carbon also, for there is an evo- 

 lution of marsh gas which contains carbon. But 

 in this slow fermentation taking place under the 

 water in peat bogs and marshes the carbon loss 

 is relatively small ; the woody material does not 

 become completely oxidized, as it does in free 

 operations of decay. The loss of hydrogen and 

 oxygen from the mass is greater than that of 

 carbon, and the percentage of carbon therefore in- 

 creases. This is not the ordinary kind of fermen- 

 tation that goes on in vegetable accumulations. 

 It requires special conditions and possibly special 

 kinds of fermenting organisms. Peat is not 

 formed in all climates. In warm regions, or 

 where the woody matter is freely exposed to the 

 air, the fermentation of vegetable matter is more 

 complete, and it is entirely destroyed by oxida- 

 tion. It is only in colder regions and when cov- 

 ered with water that the destruction of the organic 

 matter stops short of decay. But such incom- 

 plete fermentation is still going on in many parts 

 of the world, and by its means vegetable ac- 

 cumulations are being converted into peat. 



This formation of peat appears to be a first 

 step in the formation of denser coal. By a con- 

 tinuation of the same processes the mass becomes 

 still more dense and solid. As we pass from the 

 top to the bottom of such an accumulation of 

 peat, we find it becoming denser and denser, and 



