i88 



FARMYARD MANURE 



[chap. 



low that losses of ammonia would take place by 

 volatilisation, especially as the temperature was high. 

 The later analyses, taken when the heap was well 

 consolidated and kept moist, show that a steady 



Table LI 1 1.— Composition of Gases in Dunghill (Deh^rain). 



anaerobic fermentation of carbohydrates into equal 

 volumes of carbon dioxide and marsh gas was then 

 going on, while the evolution of hydrogen had stopped. 

 From these and the other analyses executed by 

 Deherain, it may be learnt that the main anaerobic 

 fermentation which takes place when the straw and 

 other materials are fresh, is that which gives rise to 

 hydrogen and carbon dioxide ; if the heap gets too 

 dry and air penetrates, an aerobic fermentation begins, 

 which gives rise to carbon dioxide only ; but at the 



