OXIDATION OF ORGANIC COMPOUNDS. 463 



humates or other organic salts These soluble materials thus held by the 

 presence of the humic acid are important plant foods. Therefore, humic 

 acid for many reasons furnishes favorable conditions for further luxuriant 

 plant growth, and these plants again react in a powerful way in promoting 

 the alterations of the belt of weathering. 



The process of decomposition of the other carbon- and hydrogen- 

 bearing compounds, aside from cellulose, especially the decomposition of 

 the carbohydrates, is described by Fischer as a fermentation. In this 

 work, as in the decomposition of cellulose, the mold fungi, as well as 

 bacteria, are at work in connection with oxygen and moisture." 



While during the history of the earth by far the larger portion of the 

 cellulose formed by organic agencies has been oxidized as above described, 

 from time to time to the present, and in various areas, districts, and regions, 

 this process has been only very partial. As a consequence, the unoxidized 

 cellulose has been buried below later sediments, and thus immense quantities 

 of carbon compounds have been entombed within the earth. This is the 

 main source of the coals, oils, peats, and carbonaceous sediments. It is 

 therefore evident that the total quantity of this entombed organic matter is 

 enormous. By metamorphism of the cellulose these carbon compounds 

 pass into the various forms of coal. After these carbon compounds are 

 formed, as a result of denudation they may again pass into the belt of 

 weathering, and here they are subject to the same oxidizing agencies which 

 are at work upon the original cellulose. But they are now in a more 

 refractory form than the original cellulose, and while the process is doubtless 

 very slow, there is no doubt that the oxidation of the coal and other similar 

 carbon compounds takes place to some extent in the belt of weathering 

 under natural conditions and thus produces carbon dioxide. But, so far as 

 I know, this process has not been studied, and I can make no definite 

 statements in reference to< it. It is probably more rapid than is commonly 

 supposed, and the changes are perhaps accelerated by oxidation of sulphides. 



Since man began to use coal, peat, and oil, artificial oxidation of the 

 cellulose and the entombed carbon compounds has taken place upon an 

 immense scale. While this method of oxidation of these carbon compounds 

 was trivial until the middle of the eighteenth century, when coal was 

 first applied to the manufacture of iron, it has since that time steadily 



« Fischer, Alfred, The structure and functions of bacteria, trans, by A. Coppen Jones, Clarendon 

 Press, Oxford, 1900, pp. 107-115. 



