112 



A. Pecller- — On (lie past and present 



[No. 2, 



Taking the results obtained by the Total An-iponia Test, and judged 

 by the standards which have been put forward by Prof. Wanklyn, and the 

 additional somewhat rougli ones suggested by myself, it will be seen, as 

 might be expected, that no single tank or well water was of extraordinary 

 organic purity, and that there were only seven tank waters included under the 

 head of " safe" waters, five of which were from tanks on the maidan. Of 

 dirty waters there were 26 out of the 200 or 13 per cent. ; of waters con- 

 siderably contaminated with sewage matter 61 Avere found, or 32 per cent. ; 

 of dilute sewages there were 32, or 16 per cent. ; and of real genuine 

 sewages 71 were found or 35-1 per cent., that is rather more than one 

 third of the whole number. 



In the following table these results are separated into the two classes 

 of tank and well waters, and it will be seen that the impurity of both 

 descriptions of waters is nearly equal when judged by this test. 



° ° ^ 



W ^ O 



Isi 



CD 



in 



Tank waters, ... 

 Percentage, 



Well waters, ,, 

 Percentage, 



Percentage of both 

 well and tank 

 water, 



52 

 42 



19 



25 



3.5^ 



o 



<D 



19 

 15 



13 

 17 



16 



O "5 tS 



^ § ° A 



r5 5 g a 



O CS M P, CS 



36 

 30 



28 

 37 



32 



c 



10 

 7 



16 

 21 



13 



g 3 3 



o o C 

 ci o 



-*=' o 



a; -So 

 >_ 





 





 



3i 



In considering the quantities of chlorine present, notice must be taken 

 of the fact that in a well water the amount of chlorine will be relatively 

 greater than that of the total ammonia derived from the organic matter, 

 because in the filtration of the water through the soil to reach the well, 

 all the insoluble portions of the organic matter present in the sewage, etc., 

 will be stopped, whilst the chlorides will readily pass through in solution. 

 Again in the filtration of contaminated water through layers of earth or 

 soil, a certain proportion of the organic matter will be oxidized and convert- 

 ed into inorganic compounds such as nitrates, which will not yield any 

 ammonia on distillation with alkaline potassium permanganate. Thus we 

 may expect, that a larger proportion of the well waters will be condemned 

 by the chlorine process than would be condemned by the total ammonia test. 



