out of the river, but the chloride content at Station 200 was lower than 

 at five of the outlying stations. On September 11 there wa? a weak 

 current upstream at the time of sampling, althou§;h the current had been 

 out and toward the north earlier, as indicated by the color of the water. 

 Yet the water at Station 202, which was obviously from the river, had 

 the lowest chloride content of any station sampled on that date. 



It must be admitted that the data on chloride are perplexing; in 

 several cases they are contrary to expectation. That is, we should ex- 

 pect the chloride to be higher at the mouth of the river than at the out- 

 lying stations, particularly when the current was flovdng out of the 

 river. One might be inclined to believe that there had been some 

 accidental transposition of samples or records in the laboratory, if it 

 were not for the fact that this could account for only a fev; of the 

 anomalies. 



The data on the different forms of nitrogen are more in accord 

 with expectation, although some unusual features are noticeable. Free 

 ammonia was commonly very low even when accompanied by high albuminoid 

 anmonia, as at Station 200 on August 8, l6, and 30, and at Stations 200 

 and 202 on September 11. The largest amount of free ammonia was found 

 at Station 213 on Auf,ust 30, when albuminoid ammonia was relatively low. 

 On the average, there was somewhat less than tvd.ce as much free ammonia 

 in this section as in the Island Section. Albuminoid ammonia was higher 

 at Station 200 than at the others, except on September 11, when the 

 discharged water had been deflected northward to Station 202. On the 

 average, there was about twice as much albuminoid ammonia in this section 

 as in the Island Section, but on August 30, Stations 211 and 2l5 showed 

 less than the mean for the Island Section. Nitrite was consistently low, 

 as was nitrate, except at Stations 211, 213, and 117 on September 11, 



In spite of the peculiarities of the data in this section, 

 there is no doubt that the water of the river is polluted and that it 

 affects the lake water in the vicinity of the mouth. Comparisons with 

 the data in Tables 33 and 26 show that River Raisin is less heavily 

 polluted than Maumee River, but more heavily polluted than Portage River. 



In general, free and albuminoid ammonia were higher in the 

 River Raisin Section than in the Island Section, vrfiile nitrite and nitrate 

 were lower. A similar condition has already been noted in the Portage 

 River and Maumee Bay Sections. It was suggested that the great abundance 

 of plankton, resulting fmm the large amount of available free ammonia, 

 was responsible for the reduction of nitrite and nitrate. The same explan- 

 ation may be offered in the case of the River Raisin Section, At Station 

 117 in 1930 the phytoplankton was four times as abundant as in the 

 Island Section (Table 62), It will be noted in Table UO that the con- 

 centration of free ammonia was not always great,, but almost without ex- 

 ception the potential supply, as indicated by the albuminoid ammonia, 

 was great. The amount present in the water is not an exact measure of 



120 



