E. J. Russell and E. H. Richards 511 



The details of the analyses are given in Table IX, but to facilitate 

 discussion some of them are given in diagram form in Figs. 2 — 5. 



Compact heaps under cover. We begin with this as the simplest 

 case. The most complete degree of compactness was attained in a 

 heap of cow manure where there was sufficient faecal matter to allow 

 the heap to be plastered down and made thoroughly solid. The 

 temperature remained throughout sufficiently low to prevent serious 

 evaporation. The heap was then left for the period Jan. to April, 1914 : 

 various changes took place which may be summarised as follows, the 

 initial quantities in each case being put at 100: 



Total dr}^ matter ... 



Total nitrogen 



Including nitrogen as NHg 



„ „ amide 



,, ,, othei' com- 

 pounds 71 76 +5* 



Maximum temperature attained 9° C. 

 * + indicates a gain in this and subsequent tables. 



The results are set out in diagram form in Fig. 2. 



During the period of storage there was a considerable evolution of 

 gas, — mainly of carbon dioxide, marsh gas and hydrogen. A sample 

 drawn from the middle of the heap has the following percentage com- 

 position : 



CO, Combustible gas (CH4, Ha, etc.) N, O2 



73 26 1 NU 



The nitrogen compounds underwent certain transformations but 

 suffered no loss in total nitrogen : this is an extremely important 

 point which will be more fully discussed later on. The ammonia 

 decreased in amount, but the "other compounds" showed a correspond- 

 ing increase, indicating a conversion of ammonia into more complex 

 substances. This particular change is not common in cow or bullock 

 manure, and we found no further instances of it in the manure heaps 

 although it occurs with horse manure and we also observed it in the 

 laboratory experiments. The important conclusion to be drawn from 

 the experiment is that no loss of nitrogen occurs under these conditions. 

 This heap, however, was wholly exceptional. The other compact 

 heaps that we put up all showed a loss of nitrogen, and differed only 



