XC11. . ABSTRACT OF PROCEEDINGS. 



curves and figures the engineer can see at a glance whether 

 any given change in composition can be accounted for by 

 rains, floods, drought or outside contamination. Chemical 

 analysis allows of inquiry as to the origin of pollution to be 

 made much quicker than would be the case if the biological 

 methods were alone accessible. 



Mr. Houghton, m. inst. ce., exhibited a diagram shewing 

 the storage capacity of unflltered water, the area of storage 

 reservoirs, and the area filtered per million gallons of daily 

 supply for the month of June last, for five of the London 

 water companies, to shew that some companies favour large 

 storage and a quick rate of filtration, and others smaller 

 storage and a slower rate. The average rate varied from 

 0*98 to 2*22 gallons per square foot per hour. He quoted 

 Dr. Frankland's figures to shew the great value of sedimen- 

 tation in storage water, which in the case of the companies 

 just quoted, shewed a reduction of bacteria from about 

 76*7 per cent, in 13 days to 92*9 per cent, in 6*3 days. 

 He thought that the author's description of the action of 

 a sand filter-bed was not quite correct, but that it is rather 

 a breaking up of the water into small particles so that it 

 comes more into contact with the bacteria in the pores of 

 the sand, in support of which he quoted Gill on the filtration 

 of the Muggel Lake Water Supply. He disagreed with the 

 statement that water containing more than 100 germs per 

 ccm. is not sufficiently cleansed, and that water should not 

 be condemned because of the number of bacteria it contains, 

 instancing the fact that water drawn from the taps in 

 Melbourne contained on a average of 199 examinations, 

 154 bacteria per ccm. He thought he was the only engineer 

 that had any experience of mechanical filters in Australia, 

 and when he was asked to advise the Broken Hill Water 

 Supply Oo. on the best means of purifying the water the 

 analysis of the water supplied to him shewed solids varying 



