2 SMALL WATER SUPPLIES. 



bered, the number being referred to in the advice 

 note with such information as date, time, place, 

 temperature of water and atmosphere, and the name 

 of the collector of the sample, etc. 



A first-class chemist will not usually consider any 

 samples which are not collected as advised. With 

 river water single samples are insufficient ; a series 

 of samples must be collected over a considerable 

 period, bearing in mind the condition under which 

 they were taken, because flood waters and waters 

 flowing after a long drought are often very different 

 from the analyst's point of view, besides such items 

 as agricultural operations, decay of plant life, etc., 

 which often have a marked effect. 



When a bacterial examination is to be made the 

 bottle should be filled with hot water raised gradu- 

 ally to boiling-point. The water is then emptied 

 and the 'bottle kept for half an hour in boiling water, 

 the stopper being kept in the bottle. 



Water has a great power as a solvent ; in fact 

 it has a greater combining tendency than any other 

 compound, although as an oxide it is indifferent. 

 It is very susceptible to pollution and will dissolve 

 gases present in the atmosphere, and in towns bring 

 down fine particles of carbon and dust from the air 

 when falling as rain. In fact there are so many 

 ways in which water apparently pure can be polluted, 

 that the greatest care must be exercised in selecting 

 any particular source of supply for domestic and 

 internal use. For country houses river water is 

 sometimes very handy. While the analyst is looking 

 into the matter it is the duty of the engineer to 

 examine the stream upwards for outward and visible 



