' 
a! 
472 Mr Saunders, The Ammonia Content of 
on the four days previous to this, ‘63 inch. After this the rain || 
did not fall so heavily but it still continued to be wet weather 
until 12 April, when there commenced a period of 10 days | 
without rain. On 14 April the ammonia content was ‘082—still 
very low. On 21 April the amount had risen to 175. I think | 
that there can be no doubt that the rainfall is influencing the | 
ammonia content, since a rapid drop in the ammonia follows | 
closely on heavy rains. There is also an increase during a dry ! 
period but the increase takes very much longer to manifest itself | 
than does the decrease. The annual cycle in which the ammonia / 
content rises to its maximum in the winter and falls to 2 minimum (| 
in the summer cannot be explained as being due to the rainfall, for ) 
it is during the winter maximum that the greatest rainfall occurs. : 
All that the rainfall does is to cause fluctuations. 
Variations in the Ammonia Content in different layers | 
of water. | 
i 
In small ponds, even though they may be only a few feet deep, 
there are differences in the ammonia content between water 
collected from the surface and water collected from just above | 
the bottom. On 17 March the water in a pond contained | 
‘138 grs. p.m. NH, at the top and ‘088 at the bottom. On || 
18 March, in the same pond, there were (075 at the top and ‘05 at | 
the bottom, and again on 21 April there were 15 at the top and | 
‘175 at the bottom. 7 
Variation in Ammonia Contents of different ponds. 
Ponds that are liable to sewage contamination contain large « 
and very varying quantities of ammonia, while others which are 
uncontaminated contain a smaller quantity and the range of | 
variation from pond to pond is very much less. Thus in different © 
uncontaminated ponds on different dates the quantities of ammonia / 
were ‘180, ‘210, ‘310, and -400, whereas in different contaminated | 
ponds the quantities were 1:65, 3:020 and 16°200. 
| 
Variations in the Ammonia Content produced artificially. | 
In the Laboratory I have four aquaria, two of which are © 
aerated, one by a rapid and the other by a slow stream of air, and — 
two others which have no aeration, one of which is left standing © 
and the other has a plunger in it working up and down so as to | 
keep the water in motion. The two which are aerated always © 
| 
have less ammonia in them than do those which have no aeration. 
It seems to make very little difference whether the aeration be | 
rapid or slow, nor does the plunger which stirs the water make — 
