XCV1. ABSTRACT OF PROCEEDINGS, 



clear of fallen timber and vegetation, the odour of the 

 water was extremely obnoxious. In other reservoirs and 

 in settling ponds numbers of rats and mice were observed. 

 These references, together with the remarks made by other 

 speakers on the presence of algae would point out the 

 necessity for filtration, but there are other very grave 

 dangers of pollution arising from the presence of the dead 

 bodies of cattle and sheep which invariably find their way 

 into the watercourses at times of drought, and are washed 

 down to the reservoir at the first flood; in districts affected 

 by pleuro or tuberculosis the water which flows off the 

 pastures must be more or less contaminated, and it is con- 

 ceivable that hydatids would be found in any reservoir; 

 even the Sydney Water Supply canals are extremely liable 

 to this form of pollution. The presence of rabbits in large 

 numbers is a danger prevalent everywhere in the State to 

 the purity of the water supply, and the discovery of dead 

 rabbits in the canals above Prospect sufficiently emphasises 

 the necessity for the filtration of all water destined for 

 human consumption. 



The question of the great variation in depth of media 

 adopted in tlie various waterworks in England is deserving 

 of some comment, as it seems to indicate some want of 

 knowledge in guiding principles. It is generally understood 

 that the top film of sedimentary and organic mud on the 

 surface of the sand performs the principal duty of strain- 

 ing and interception of bacteria, while the sand beneath 

 the film performs in a lesser degree the same duty, its 

 principal function being the support of the film, the aeration 

 of the passing water and the generation of water bacteria, 

 which Piefke has demonstrated to be of great importance 

 in the satisfactory working of the filter. The relative 

 proportion of the duty performed by the several parts of 

 the media has been experimentally determined by Dr. 



