On each of the first three dates in Table 36, the current was downriver, 

 but the chemical c^^nditions at Station 200 differed markedly on the three 

 dates. There was no oxygen in the -later on August 30, while on August l6 it 

 was 38 per cent saturated, and on August 8, 63 per cent saturated. There 

 were corrssponding differences in free carbon dioxide and pH. These differ- 

 ences suggest that the direction of the current prior to the time of sampling 

 is an important factor in determining the condition of the w ater discharged 

 from the river. Presumably the current had been out of the river for some 

 time before sanpling on August 30, so that the outgoing water was river water 

 undiluted by water from the lake. On August 8, it is probable that the direc- 

 tion of the current had just changed and the discharged water was a mixture of 

 river and lake water That this explanation is the true one is further indi- 

 fated by the fact that methyl orange alkalinity wa- highest when the oxygen 

 was lowest, and lowest vrhen oxygen was highest. In the discussion of the 

 Mauraee Bay Section it was noted that the river water was mugh higher in car- 

 bonates than the bay water. Here, too, carbonates were higher in the river 

 than in the lake on the days when the current was outgoing, and it is reason- 

 able to suppose that the magnitude of the difference would be a rough measure 

 of the amount of mixing which had taken place in the volume of water being 

 discharged at the tiiie of sampling. 



The samples taken north, south, and east of Station 200 on August 8 and 

 l6 showed no evidence of contamination by river water. It is true that the 

 lake water was not saturated with oxygan, but both days were cloudy and prob- 

 ably there was little photosynthetic activity. On August 30, the sarrole 

 taken one-half mile south of' the river evidently was affected by river water, 

 as shown by the low oxygen and pH, and high free carbon dioxide as compared to 

 other samples from the lake. It is worthy of note that this ample had higher 

 methyl orange alkalinity than the other lake samples. August 30 was also a 

 cloudy day, which accounts for the rather low oxygen content at the other sta- 

 tions in the lake. 



A peculiar situation was encountered on Septanber 11. At the time of 

 sampling, lake water was flowing into the river, but a mass of turbid water 

 was seen north of the river. That this turbid water had been discharged 

 from the river is s'lown by the chemical determinations. Water in the mouth 

 of the river was nearly saturated with oxygen, while at Station 202, one- 

 half mile north, it was *^^jnly 38 per cent saturated. In fact conditions at 

 the latter station were almost identical with those at Station 200 on 

 August l6. The river water had not reached as far north as one mile, as 

 shown b" the data for Station 20[i. The high content of oxygen at all sta- 

 tions except Station 202 is explained by the fact that the sky was cloudless, 

 permitting the maximum activity of chlorophyll-bearing organisms. 



Samples were taken at Station 200 on two dates not shown in the table, 

 namely, July 30 and Sentember 30. There was no current on either day. On 

 July 30, the water was 55 per cent saturated with oxygen, and on September 30, '. 

 it was 7^1 per cent saturated. No samples were taken in the lake near the 

 river on these dates. 



