OF WATER FOR ORGANIC MATTER. 57 



are formed, and the original organic matter. The ni- 

 trites, not being fully oxidized, are supposed to be in the 

 process of becoming nitrates. They have been taken, 

 therefore, as indicating recent organic matter, — the word 

 " recent ^' meaning only that they stand between the 

 organic matter and the nitrates. I do not know that 

 nitrates are converted into nitrites in water. 



In looking for organic matter, I think it quite unsafe 

 to trust either to chemistry or the microscope, without 

 giving time for the development of all possible germs ; but 

 this is a point which demands a good deal of inquiry. 

 Microscopists have given us details of appearances; but 

 these have not been sufficiently classed ; and the conclu- 

 sions drawn have, therefore, not been valuable to the 

 desired extent. To trust to the microscope without time 

 for development, is to believe that the germs of disease 

 can be seen. The use of allowing it to stand is not that 

 the germ of disease may be seen, as we do not know 

 it if we see it, but to see if the matter is active. The 

 value of this must be tested. 



The gases of pure water contain nearly 34 per cent, of 

 oxygen. 



Dalton found cistern-water almost entirely deprived of 

 its oxygen ; and I have found every percentage of oxygen 

 from 34 downwards. 



I go further into this point in my chapter on water, 

 which I hope to bring out soon. Meantime I may say 

 that the examination for oxygen is a very important one. 



The loss of the oxygen with peaty matter and no vege- 

 tation indicates, as already said, the formation of carbonic 

 or a bitter acid. The loss of oxygen with the evolution 

 of sulphuretted hydrogen indicates putrefaction ; but there 

 are two conditions which externally resemble each other 

 very much, namely, the growth of vegetable matter with 

 diminished oxygen, and the growth of vegetable matter 



