390 



Dr. P. F. Frankland. 



[June 18, 



consisted of ten such cylinders, and the water (ordinary Thames 

 water) was forced through under a pressure of between 30 and 40 feet 

 of water. Under these circumstances the filter commenced by yield- 

 ing 1 litre in 40 minutes, or 36 litres per 24 hours, but already at the 

 end of a fortnight's continuous action it was only delivering 1 litre in 

 1 hour 14 minutes, or rather less than 20 litres per 24 hours ; and 

 after 2J months the rate of filtration was 1 litre in 1 hour 22 minutes, 

 or 17i litres in 24 hours. 



The water both before and after filtration was examined for micro- 

 organisms with the following results : — 



Thames water 54 centres per c.c. 



„ after filtration. . 



The water before and after filtration was also submitted to chemi- 

 cal analysis with the following result : — 



Results of Analysis expressed in Parts per 100,000. 



Thames water. 



Before filtration. After filtration. 



Total solid matters 33 70 



Organic carbon *282 



„ nitrogen '028 



Ammonia 



Nitrogen as nitrates and nitrites '288 



Total combined nitrogen *316 



Chlorine 1 9 



Temporary hardness 15 * 7 



Permanent ,, 4 *9 



Total „ 20-6 



Both samples were clear and palatable 



30 '04 

 •284 

 •027 







1 



14 



5 



19 7 



•289 

 •316 

 •9 

 •4 

 •3 



It thus appears that although this filter, when new, effects the 

 complete removal of the micro-organisms in the water, it has but a 

 very trifling influence upon the chemical composition of the water, 

 the only change in this respect being a slight diminution in the 

 amount of mineral matter present. 



Micro-organisms in Potable Water. 



I have also submitted numerous samples of natural waters of different 

 origin to examination for the number of micro-organisms which they 

 contain. My investigation in this direction is, however, still far from 

 complete, but I append the results which I have obtained from a 

 monthly examination of the various waters supplied to the Metropolis 

 during the present year. When the history of the water is accurately 



