Chemical Changes in Miatures of Sewage and Sea-Water, 345 
students were at work, and where at times a good deal of ammonia 
was present in the air; and, secondly, during the long period 
over which the experiment extended, some evaporation of the 
mixture of sewage and sea-water must have occurred (although 
the jar containing it was covered). 
But, on the other hand, the increase in nitrogen continued 
after the vessel containing the mixture had been removed to a 
room specially reserved for water analysis where no free ammonia 
could be present in the air (beyond the amount normally found in 
it), to such an extent as cannot be accounted for by the second 
_ cause mentioned. As this investigation is of a preliminary 
character, further discussion of the matter may be deferred until 
more experimental data are available. Meanwhile it seems obvious 
from our experiments that the nitrifying organism can grow in 
sea-water, and that the changes which occur when putrescible 
substances are in contact with the latter are probably of the same 
nature as with fresh water. 
The fact, however, that such a large proportion of free 
ammonia remained unnitrified after so long a period as eleven 
months is remarkable. 
