Water Supply of Belfast. 6 7 



or not, but the experiments of Koch and Pasteur have estab- 

 Hshed the fact that micro-organisms abound in waters highly 

 charged with organic matter — in other words, the latter forms 

 the nutriment for the micro-organisms. Hence, the less 

 organic matter we have in a drinking water the fewer micro- 

 organisms are likely to be present. The opinion is fast gaining 

 ground that microbes have an active part in creating and 

 spreading zymotic diseases, and this opens up a very wide field 

 for discussion. Are all micro-organisms harmful to the human 

 system, or only certain kinds of them ? or are they only 

 injurious in certain receptive states of the human subject, or 

 perhaps in certain inflamed states of the microbes themselves 

 after too free an indulgence in organic matter ,? These are 

 questions of a highly interesting character, but we cannot stop 

 to discuss them. Dr. Frankland has shown, however, by very 

 numerous experiments, that in sand filtration the colonies of 

 microbes are reduced to an extent ranging from 50 to 100 per 

 cent., and that, within certain limits, the intercepting power is 

 inversely as the speed of filtration. Why the upper surface of 

 a layer of sand with pores large enough to be visible to the 

 naked eye should intercept micro-organisms of which clusters 

 of millions are invisible, is a question I cannot answer, and I 

 leave it with the observation that the coating of sediment upon 

 the top of the sand, which is more or less organic in character, 

 forms a nutritive environment for the micro-organisms. Pos- 

 sibly the latter collect there rather than investigate the sterile 

 regions lower down. It thus appears that with a well con- 

 structed sand filter, and regular redressing, water can be con- 

 siderably improved in quality. The organic matter is reduced 

 in quantity, and the micro-organisms to a very large extent 

 intercepted. 



The works which I have briefly described will cost, in all, 

 about ;^7o,ooo, and will be capable of filtering 11^ million 

 gallons per day. The working expenses and annual cost of 

 capital will come to about jf 3,650 per annum, or about ^10 per 

 day. This works out at 17s. 4d. as the cost of filtering one 



