OF WATER rOR ORGANIC MATTER. 55 



albumen^ or in a substance removed a step from albumen 

 and passing downwards to a condition more allied to the 

 idea of an inorganic body. 



I have given my reasons for believing that neither the 

 nitrogen of ammonia nor the nitrogen found in peaty 

 water can be taken as the slightest indication of the 

 amount of putrescible matter. At present^ I believe,, we 

 have no idea of the actual relation in which it stands to 

 health. It will be interesting to know now if the nitrogen 

 of the nitrates and nitrites is at all similar. These salts are 

 not formed when putrefaction is going on rapidly. The 

 reason is very simple : the water is then deprived of its 

 oxygen. We do not know all the conditions of the forma- 

 tion of these salts ; but one is essential, that oxygen shall 

 be present. 



In the Thames water, at least two miles below and above 

 Hungerford, there was nitric acid in considerable abun- 

 dance in 1848. It is mentioned, in evidence given in a 

 parliamentary inquiry twenty years before that, that red 

 fumes rose on heating the deposit. I quote from memory. 

 In 1848 this was certainly the case. In later analyses, 

 by Dr. Hofmann, the nitric acid was not mentioned. I 

 considered this at the time a great mistake; and I ex- 

 amined the water again, finding extremely little nitric 

 acid, and, I believe, in some cases none. 



Having examined other putrid streams, and found no 

 nitric acid, I conclude that it had disappeared from the 

 Thames also when it became more impure than pre- 

 viously. 



During the time that river was so offensive near the 

 Houses of Parliament, the organic matter must have 

 wholly, or nearly so, deprived of its oxygen the air in 

 solution. Running streams, however, do not, so far as I 

 know, contain much nitric acid ; that substance is formed 

 in greatest quantity by the action of porous substanccKS. 



