54 WATER 



(contrary to instructions)' and the trenches were not filled with rock 

 and earth as carried out for spring No. 2. When this bracken 

 was removed and the trench satisfactorily filled with rock and 

 earth these springs yielded bacteriologically pure water. 

 The analyses made were as follows : 



Organisms per c.c. 



at at B. coli Streptococci 



Source Date 37 C. 2iC. (per litre) 



No. i Spring Nov. 1912 6 30 1000 10,000 1000 10,000 



(atypical) 



2 ,, ,, ,, 13 35 absent in 50 c.c. absent in 50 c.c. 



,, 3 ,, ,, ,, 8 25 1000 10,000 100 1000 



(atypical) 



,, i ,, March 1913 2 5 absent in 50 c.c. absent in 50 c.c. 



" 3 > 5> 4 > > 



Admixture with surface water is particularly liable to occur 

 in samples of spring water taken in connection with proposed 

 new sources of water supply, since in such cases usually the only 

 samples which can be collected without expense are those ad- 

 mixed with surface water where the spring outcrops. 



The following is an interesting illustration of the value of 

 careful investigation of deep water supplies and the use of 

 bacteriology to detect surface contamination. 



The public water supply of a small town showed on bacterio- 

 logical examination distinct evidence of contamination (sample 

 No. i below). The supply was derived from three springs in the 

 old red sandstone, the water being conveyed to a brick-covered 

 reservoir (36,000 gallons capacity) by agricultural pipes. A 

 separate analysis was made of the water from each spring (Nos. 2> 

 3 and 4) while a further analysis of the water in the reservoir 

 (No. 5) was still not satisfactory. The springs were, as shown 

 from these and other analyses, mostly satisfactory and the un- 

 satisfactory condition of the supply was due to surface water 

 passing into the pipes and so into the main supply. Another 

 spring known to be liable to some contamination and excluded 

 from the supply was examined (No. 6) at the same time and 

 shown to be unsatisfactory. Steps were taken to put in proper 

 pipes and cut off all surface water and the latest analysis (No. 7) 

 was quite satisfactory. 



