42 DR. R. ANGUS SMITH ON THE EXAMINATION 



some form of putrefaction will be the only result; but 

 whether this occurs alone, or along with organized forms_, 

 an excess of organic matter is proved. 



^^ Water that will not bear the test of standing will in 

 most cases be rejected at once. If no other can be ob- 

 tained, it ought to be used before the putrefactive process 

 has begun; but this is very dangerous. The next best 

 method is to wait till after putrefaction has terminated, 

 and the products are separated as much as possible. This 

 is popularly known to be the case when the water has for 

 some time become clear and colourless, and free from 

 smell and taste. 



"Water with green organic matter in suspension or 

 semisolution is generally full of germs of living things 

 and nauseous to the taste. 



^'A microscope is very useful in detecting the smaller 

 forms of life. Good water is clear and colourless, or only 

 slightly browned by peat. Clear bright water shows no 

 microscopic objects. It is quite a mistake to suppose that 

 all water contains animalcules. Those who have sent abroad 

 this saying could not have known what pure water is. 



" If the signs of organic matter are clear, it may not be 

 needful to go further, but to reject the water at once. 

 After standing for two or three days, varying with tem- 

 perature, and showing nothing to the eye except a little 

 film of green on the bottom of the vessel, we may conclude 

 that not much organizable matter is there. We may then 

 proceed to the chemical examination.^^ 



Some years ago it was customary, more than now, to 

 examine with the microscope water intended for the use of 

 towns. Attempting at one time to join the chemical and 

 microscopic together, as they were too much in separate 

 hands, I came to certain general conclusions : — That no 

 ordinarily pure water produced much vegetable or animal 

 life, and that microscopists were mistaken in allowing 



