364 



H. M. Vernon 



for analysis, the remainder was put into a smaller flask, so tbat there 

 was still very little exposure to the air. The results of the chemical 

 analyses were however practically the same as before. 



In each case we see that the free ammonia present varies a 

 great deal, though after 10 or 12 days it is considerably diminished 

 in amount, whilst on the other band the organic ammonia is largely 

 iucreased. These changes in the composition of the water are due, 

 at any rate in part, to the vegetable growth wbich begins to form 

 after a few days on the sides of the vessels, in spite of the exposure 

 to the sun, and the high temperature wbich the water thereby attains. 

 For instance, the temperature of the water in the jar was noticed 

 once or twice to be as high as 38°, and that of the flask, 35°. 



Chemical analysis therefore fails to show much difference between 

 the efifects of exposure of the water to the sun alone, and to exposure 

 to the air in addition: but on growing larvte in specimens of water 

 treated in these two ways, the difference is extremely marked. 



