1885.] The Removal of Micro- Organisms from Water. 391 



known, and due precautions in collecting samples have been taken, 

 there can be no doubt that in many cases it is capable of throwing 

 considerable light upon the quality of water and in assisting to 

 interpret the results of chemical analysis. 



The method of collecting samples which has been employed by me 

 is the following : — 



Small (about 3 oz.) bottles, accurately stoppered, and sterilised by 

 being heated to 150° C. for at least three hours, are kept tightly 

 stoppered until they are to be used. In taking the sample, the out- 

 side of the bottle is well washed in a stream of the water to be 

 examined, the stopper is then removed, the bottle nearly filled with 

 water, and the stopper replaced as rapidly as possible. The examina- 

 tion of the water should follow as soon as possible after collection. 



The following results were obtained with samples taken as above 

 from the mains of the various companies supplying London : — 





~No. of centres per c.c. of water. 



J anuary. 



February. 



March. 





8 (Oliq.)* 



23 ( 2 liq.) 



10 ( Oliq.) 





2 (Oliq.) 



16 ( 2 liq.) 



7 ( liq.) 





13 (Oliq.) 



26 ( 2 liq.) 



246 ( 1 liq.) 





382 (4 liq.) 



57 (23 liq.) 



28 (12 liq.) 





10 (2 1iq.) 



5 ( Oliq.) 



69 ( lliq.) 





7 (4 liq.) 



7 ( Oliq.) 



95 ( 1 liq.) 





25 (Oliq.) 



39 ( Oliq.) 



17 ( Oliq.) 





10 (Oliq.) 



41 ( Oliq.) 



9 ( lliq.) 



* Liq. denotes that the organisms caused liquefaction of the gelatine. 



It would be premature to draw any conclusions from these results, 

 and I purpose to continue these observations over a longer period of 

 time. 



The waters were also at the same time submitted to chemical 

 analysis, so that their biological and chemical characters might be 

 compared ; the results are given below. 



General Conclusions. — (1.) Of the substances experimented with, 

 only greensand, coke, animal charcoal, and spongy iron were found to 

 wholly remove the micro-organisms from water filtering through 

 them, and this power was in every case lost after the filters had been 

 in operation for one month. With the exception of the animal char- 

 coal, however, all these substances, even after being in action for one 

 month, continued to remove a very considerable proportion of the 

 organisms present in the unfiltered water, and in this respect spongy 

 iron and coke occupy the first place. 



