

Hydrogen. 



Oxygen. 



Nitrogen. 



6.21 



43.03 



1.10 



5.50 



33.00 



2.00 



THE PENNSYLVANIAN PERIOD. 569 



now is in Dismal Swamp, and in many other less well-known swamps 

 and bogs. In and about marshes and swamps we therefore find the 

 conditions for the accumulation of considerable thicknesses of vegetable 

 matter, essentially free from sediment, and at the same time the con- 

 ditions which keep it from decay. 



But while the vegetable matter is not destroyed, it is not preserved 

 intact. The composition of wood and peat are illustrated by the 

 following analyses (the ash is omitted), though it is not to be under- 

 stood that either wood or peat has a constant composition. The 

 difference, it will be seen, is not great. 



Carbon. 



Wood 49 . 66 



Peat 59.50 



The relative atomic proportions of carbon, hydrogen, and oxygen 

 in wood are approximately expressed by the formula C6H9O4. In 

 the air, the carbon and the hydrogen of the wood unite with the oxygen 

 of the air or of the wood itself, forming carbon dioxide and water, 

 the principal products of the decay of vegetable matter. But under 

 water, the atmospheric oxygen is largely excluded, and the elements 

 of the wood unite with one another to a larger extent, while the oxygen 

 of the air plays but a subordinate part. One of the common products 

 of decay under such circumstances is CH 4 (marsh-gas), which bubbles 

 up from many swamps and escapes into the atmosphere. The forma- 

 tion of this gas, as its composition shows, exhausts the hydrogen four 

 times as rapidly as the carbon. If the carbon of the wood unites 

 with the oxygen of the wood, forming carbon dioxide, the oxygen 

 is exhausted twice as rapidly as the carbon. If the hydrogen and 

 the oxygen of the wood combine, the result is to increase still more 

 rapidly the percentage of carbon remaining, so that in whatever way 

 these elements combine, the result must always be to increase the 

 proportion of carbon remaining in the solid. Even under water it 

 is probable that atmospheric oxygen dissolved in the water takes 

 part in the changes, and in so far as this is the case, the pro- 

 portion of carbon remaining after the changes have taken place is 

 diminished. 



While the exact quantitative relations of the reactions which take 

 place are not known, and are probably not constant, the following 



