5.95 parts per million. Some of this increase was due to a lowering 



of the water temperature and consequent greater solubility of oxygen, 



but, in all probability, increased dilution was the principal factor 

 involved. 



Chloride and nitrogen 



Samples were taken on six dates at each of three stations in 

 this section (Table h6) . Station 219 is in Detroit River at the 

 south end of Bois Blanc Island, near the Canadian shore. Station 126 

 is in Lake Erie, 5 miles from the mouth of the river. Station 13ii is 

 also in Lake Erie and is 13 miles from the mouth of the river. 



The chloride content of the water in this section varied con- 

 siderably on the different dates. This is particularly noticeable at 

 Station 126, where it ranged from 6,1 to 13.6 parts per million. Com- 

 paring Stations 219 and 126 on the same dates, it may be seen that they 

 were not in agreement; the lowest value was recorded for Station 219 

 on the same day as the highest for Station 126, The mean chloride at 

 Station 13U was lower than at Station 126, although the opposite re- 

 lationship is to be expected, because of the high chloride content in 

 the other sections of the lake. Obviously Station 13li must receive 

 DetT"cit River water which has undergone little or no mixture with water 

 from the open lake. The lack of agreement between Stations 13U and 126 

 is net surprising in view of the large variations in this section. It 

 merely means that too few samples were taken to show the average chloride 

 content accurately. 



The different forms of nitrogen show a rather wide range also, 

 particularly free ammonia. Yet the means at the bottom of the table 

 have some characteristics in common which are markedly different from 

 those at stations near the mouths of other rivers. In spite of the 

 small number of samples, it seems probable that the means are a fairly 

 reliable index of the character of the water with respect to the con- 

 centration of nitrogen compounds. Comparison of Station 126 with 

 Station 250 (Table 33) shows that Station 126 was much lower in free and 

 albuminoid ammonia, somewhat lower in nitrite, but higher in nitrate. 

 The results at Station 126 agree more closely with those at Station 25h 

 (Table 33), Station l59 (Table 26), and Station 117 (Table 39). Still 

 closer agreement is to be found between Station 126 and the mean of 

 stations in the Island Section (Table 22). Of particular interest is the 

 fact that the amount of decomposing organic matter, as indicated by 

 albuminoid ammonia, \ias greater at Station 126 than in the Island 

 Section, 



130 



