632 PROCEEBTNGS OF SECTION I. 



process that the Onkaparinga water could be purified at a cost of 

 about one farthing per thousand gallons, including allowance for 

 interest and depreciation on all machinery, &c., capable of treating 

 thirty million gallons per diem. The cost of treatment would be 

 less if the impure water were allowed to run into the reservoir and 

 the Avater purified for use as required, as in this case machinery 

 would be required for treating less than ten million gallons per 

 day, but I strongly advocate the former method for the following 

 reasons : — Practically no silt would enter the reservoir, and hence 

 the cost of keeping it in order would be greatly reduced. The 

 water in the reservoir would be so pure that there would be a 

 minimum of life in it, whereas with impure waters the reservoirs 

 teem with life in consequence of the abundance of food material. 

 The water alter treatment is in such a state that all suspended 

 matter quickly subsides, and the water drawn off from a depth is 

 quite sterile. (See page 13, B 2\otes.) Direct sunlight has been 

 proved to be fatal to many species of bacteria, and the purified 

 water would allow the light to penetrate to a much greater depth 

 than the impure turbid water. By long standing after treatment 

 the water undergoes considerable natural purification, and attains a 

 more natural and healthy state for use than if used directly after 

 treatment. It has been remarked that waters Irom a great depth 

 and those which have been chemically treated are not so healthy as 

 those from a moderate depth, or those which have had time to 

 attain a natural character after treatment by standing exposed to 

 the sun and air. I am unable at present to quote the autliority for 

 this statement. In addition to the above there would be a con- 

 siderable saving of water whichever system was adopted in con- 

 sequence of the smaller quantity required for flushing the mains. 

 Lastly, the expense incurred in purifj'ing the water seems to be 

 very small for such an excellent result. 



The continued use of impure waters, as the population and 

 thence the chances of dangerous contamination increases, is 

 certainly most undesirable. By adopting a system of purification 

 as soon as and wherever practicable the general health of the 

 community would certainly be improved, and it is possible that 

 some epidemic diseases would be greatly diminished in frequency 

 of occurrence, and perhaps others prevented from obtaining a 

 footing here. 



BA.CTERIOLOGICAL NOTES. 



Dr. A. B. Griffiths, F.R.S.E., &c., in a paper on "A New 

 Method for the Bacteriological Examination of Water" ("Chemical 

 News," May, 1893, page 234), says : — " In addition to the above- 

 mentioned conditions the number of microbes in any water depends 

 upon the amount of organic matter present. A water rich in 

 organic matter always contains a larger number of microbes (in a 

 given volume) than a water almost free from such matter." 



The above remark apjjiies not only to microbes, but to many 

 other forms of life, and doubtless the entrance of impure water 



