WATEE 15 



Brown waters are suspicious of sewage or other organic 

 contamination. 



The sediment forms usually after the specimen has stood 

 for twelve or twenty-four hours ; to obtain it the clear water 

 is drawn off by a syphon, and the remaining water and 

 sediment poured into a conical glass. It will usually be 

 found to consist of vegetable debris, in which may be 

 detected low forms of organic life, ova of insects, parasites, 

 etc. A microscopical examination is the only satisfactory 

 method of dealing with it. 



The lustre of a water is its degree of brilliancy ; the 

 chalk waters have an exceedingly brilliant appearance, from 

 the amount of carbonic acid they contain. The brilliancy 

 of a water may be great, slight, or nil. 



Taste. — Good water should have no taste, but the 

 absence of taste does not mean freedom from pollution. 

 Some of the worst waters from shallow wells are bright, 

 sparkling, and entirely free from taste. Iron is the only 

 substance in water which can be detected by taste when in 

 small quantities. 



S7nell. — Good water should have no smell ; the best 

 method to determine smell is to heat the water, when 

 putrefactive gases may be recognised. A good plan with a 

 suspected water is to put it in a warm place for a few days 

 in a stoppered bottle half full. Both smell and turbidity 

 may then be determined. 



The opinion formed of the purity of a drinking water 

 from the physical examination alone might be misleading, 

 as a very unpromising looking water may be perfectly pure, 

 and vice versa. We are, however, justified in considering, 

 in the absence of anything more definite, that a water 

 possessing no colour, taste, or smell, with but a slight 

 sediment and brilliant lustre, is perfectly fit for drinking 

 purposes. 



Microscopical Examination. — This is undertaken with the 

 object of determining the nature of the suspended matter, 

 and thus have a possible clue to the nature of the contami- 

 nation. But it is important to bear in mind it is not the 



Digitized by Microsoft® 



