212 Transactions of the Socief//. 



Again, although filtration through filter candles gives a sterile 

 filtrate, the water does not come through quickly enough to satisfy 

 a troop of thirsty soldiers, and then can only be obtained as 

 the result of a good deal of hard work at the pump ; and, from 

 practical experience, it is found that those who have the charge 

 of the water-carts, unless blessed with a very rigid conscience 

 and a conviction that there is infective matter in the water 

 with which they are dealing, are prone to lack care not to 

 break — or, perhaps, low be it spoken, to take care to break — 

 the filters. A cart can be filled through broken filters in less 

 than a third of the time, or at any rate with the expenditure 

 of less than a third of the energy required to drive the water 

 through the unbroken filter candles. For many years I, with 

 many others, have been seeking some method of sterilizing water 

 by means of chemical reagents — reagents which would not alter the 

 taste of the water, and would not render it flat, and that could be 

 used in quantities well adjusted to effect complete sterilization and 

 nothing more. Using ozone as a sterilizing agent I obtained 

 excellent results. Then I turned my attention to the action of 

 the ultra-violet rays as sterilizing agents. These latter are, un- 

 doubtedly, effective, but up to the present the machinery required 

 to carry out the process is somewhat difficult to manipulate, and 

 the whole process requires to be watched and regulated exceedingly 

 carefully if satisfactory results are to be obtained. The sterilization 

 of water by the addition of electrically produced ozone is, from 

 many points of view, an ideal process. It sterilizes water, or 

 rather it kills without fail the non-spore-bearing organisms which 

 give rise to cholera, typhoid, and bacillary dysentery, whilst, in the 

 quantities necessary to effect sterilization, it does not interfere in 

 any way with the taste of the water unless there is a considerable 

 quantity of organic matter present. It is, however, a somewhat 

 costly process and requires for its successful application an ex- 

 pensive plant and skilled attention. Given these it may be looked 

 upon as an ideal process, in that ozone is amongst the things that 

 are popular, and no one would think of objecting to its addition to 

 water. For poor communities the expense is, of course, prohibitory, 

 whilst for field work the elaborate apparatus and power required 

 must always constitute a difficulty. Many years ago, now more 

 than I care to number, working with Dr. Cartwright Wood, I 

 carried out a series of experiments with solutions of hypochlorous 

 acid and hypochlorites made by passing a weak electric current 

 through sea-water. We were much struck by the powerful 

 bactericidal properties of this weak solution, especially when 

 applied to the Bacillus coli communis and the typhoid bacillus. 

 Even sewage containing an enormous number of these organisms 

 had its contents of living bacteria markedly diminished, whilst 



