THE ORIGIN OF ORGANIC MATTER 57 



supplying the needs for fuel through vegetable material/"* This factor 

 is the productivity of the tropics. While agriculturalists are apparently 

 not in agreement on the potentialities of the tropics, there is no question 

 but that these regions are very favorably suited for the conversion of 

 solar energy through photosynthesis. Ikit, on the whole, the conditions 

 in the tropics are even less amenable to careful survey over a period of 

 years than the temperate zones. The question of the kind of plants best 

 suited for fuel production has received little attention, apparently even 

 as to whether these should be sugar and starch or oil producing plants. 



In the production of alcohol fuel is one of the most important items ; 

 every gallon of 95 per cent alcohol requires about 15 pounds of coal. In 

 tropical countries refuse from crops must constitute the main fuel supply. 

 In the cane sugar industry the residual fibre or "bagasse" constitutes 

 about one fourth of the weight of the canes. This waste material is un- 

 suitable for the preparation of ethyl alcohol, and as yet probably can be 

 used only as fuel directly."^ 



If alcohol is used as fuel, starting with a 10 per cent solution of alcohol 

 by weight and producing 91 per cent alcohol, about one third of the 

 alcohol produced will be required to furnish the heat necessary for distil- 

 lation."" While a solution of alcohol 91 per cent by weight would probably 

 be satisfactory for fuel, considerably more heat would be required to 

 produce 95 per cent alcohol. These and many other economic and 

 technical problems such as transportation and water supply make the 

 enterprise of fuel alcohol a very complicated one. But if in the future 

 we must look to agriculture for our industrial energy, there is no doubt 

 that the tropics will play a very important part. 



How such a state of affairs would affect the production of food it is 

 impossible to say. The temperate portions of Europe and Asia with 

 the exception of Russia are already overpopulated. Tropical Asia largely 

 is in the same condition. It is doubtful whether these as well as the 

 arable portions of the United States and Canada can be counted on for 

 anything but the production of foodstuffs. There still remain huge agri- 

 cultural areas in tropical South America and central Africa where the 

 population is relatively sparse. Whether these areas are destined to offer 

 relief to the increasing population of Europe and to over-populated Asia, 

 or can be put to other uses than food production raises economic and 

 political questions far beyond the domain of this work. 



But the relation of land areas to population is one of the most funda- 

 mental economic conditions affecting the lives and destiny of a people. 

 Hence any new factor introduced into these conditions is certain to have 

 profound consequences. The utilization of land areas in the United 

 States has been the subject of much careful study particularly by the 



«4 

 65 



Whitford, H. N., Jotirn. Ind. and Eng. Chcm., 14, 151 (1922). 

 Sherrand, E. C, and Blanco, C. W., Joiirn. Ind. and Eng. Chem., 12, 1160 

 (1920). 



** From private communication of Dr. W. H. Rodebush. 



