CHEMICAL AND BACTERIOLOGICAL EXAMINATION OF SOIL. 



767 



If we thus classify the samples, and again subdivide each of the classes into " samples 

 from a depth of 4 feet and less depths," and " samples from a depth 4 feet 6 inches 

 and greater depths," and take the mean of the ratios of nitrogen to carbon in each sub- 

 class, we find a striking fact apparent, viz., that although the organic nitrogen and 

 carbon in samples of polluted soil above the 4 feet level may be fairly large in 

 amount, yet the ratio of nitrogen to carbon is not markedly increased when compared 

 with the ratio found to exist in pure soils at similar levels. 



In the case of samples taken below the 4 feet level, however, things are very 

 different. There the organic nitrogen and carbon in polluted soils is large in amount as 

 compared with pure soils, and the ratio of nitrogen to carbon is very decidely increased. 

 The difference in the ratios is best seen in the subjoined table. 



Depths. 



Pure Soils. 



Polluted Soils. 



Relation of Nitrogen to Carbon. 



Relation of Nitrogen to Carbon. 



4 feet and less depths, 



4 feet 6 inches and greater 

 depths, .... 



1 to 8-9 

 1 to 10-25 



1 to 8-56 

 1 to 7-87 



From such a comparison one is inclined to believe that burial has but little influence 

 on the organic matter present in the upper reaches of the soil, whereas the increase in the 

 amount of organic matter and the high proportion of nitrogen to carbon in the deeper 

 layers indicates that a considerable amount of organic matter is added to these layers by 

 the decomposition of the bodies buried in the soil. It would also appear from the table 

 that the amount of ammonia present, either free or in the form of its salts, is at least a 

 rough indication of the purity or otherwise of the soil, though giving no indication of 

 the nature of the organic matter present. A large percentage of organic nitrogen and 

 carbon is always associated with a high percentage of ammonia. 



My results do not afford any indication as to what extent and with what rapidity the 

 process of " self -purification " goes on. For this it would be necessary to get numerous 

 samples from the immediate vicinity of coffins buried for varying lengths of time, as well 

 as samples at various distances above and below the coffins. A complete investigation of 

 this kind would, no doubt, prove most interesting, but would necessarily spread itself 

 over a considerable period of time, as such samples are only to be obtained on rare 

 occasions. 



This research, although it occupied the writer's time for fully eight months, does not 

 profess to be by any means an exhaustive examination of the soil of graveyards, being at 

 the best fragmentary, and merely touches on the outskirts of a subject on which much 

 interesting!: and instructive work remains to be done. 



VOL. XXXVII. PART IV. (NO. 34). 



6 A 



