Judging by the results f,iven in Table 36, River Raisin is not 

 an important factor in the chemical pollution of Lake Erie. In spite 

 of the intense pollution of the river, amounting in one case to complete 

 exhaustion of oxygen, it is evident that the discharge is too meager 

 to influence the lake water over a large area. This is well illustrated 

 by the data for September 11. At the time of sampling the current had 

 just begun to flow into the river, yet the previously discharged water, 

 which was diverted northward by a littoral current, extended less than 

 a mile from the river. This shows that the volume of water discharged 

 must have been small. Obviously the river water would soon be diluted 

 to the point where its presence could not be detected by determinations 

 of dissolved oxygen and free carbon dioxide. Aeration and photosynthesis 

 would aid in the process of recovery. 



In 1920 a large number of determinations of dissolved oxygen 

 were made in this region by an investigator working under the direction of 

 Professor Jacob Reighard. The results have never been published, but 

 Professor Reighard has made them available for inclusion in this report. 

 Only the data of particular interest here have been used. In Table 37 

 are shown the data from t^ro points in River Raisin near the mouth and in 

 Lake Erie near the river on four dates. Unfortunately no data are 

 available on the direction of the current at the times samples were taken. 



Each sample taken in the canal at a distance of three fourths of 

 a mile from the lake showed low oxygen content; the per cent of satura- 

 tion ranged from 15,36 on August 27 to ii2.06 on September lU. Samples 

 taken here on other dates indicate that the water frequently approaches 

 complete exhaustion of oxygen. At a distance of one fourth mile from the 

 lake on August 27 there was less oxygen than at the point farther up the 

 river. On September 6, oxygen was much higher at the down-river station, 

 due, perhaps, to the fact that the current had just started to flow into 

 the river. On the last two dates there was little difference in oxygen 

 content at the two points. Each of the samples taken in the lake, except 

 the one taken on September 6, showed a lower oxygen content than would 

 be expected if the water were not contaminated by polluted river water. 

 On September II4, oxygen was almost as low at a point one-half mile out 

 in the lake as in the canal itself. The oxygen content in the lake on 

 September 6 was only slightly less than in several samples taken at about 

 the same distance from the river in 1930, 



Table 38 shows data taken in the canal at Monroe Light (that is, 

 at Station 200 of Table 36) and at three points in the lake toward the 

 northeast. The station halfway to Stony Point is a little more than two 

 miles from the river. 



The results obtained on August 11, 12, and 13 are remarkably 

 uniform for each station. The water at the station corresponding to 

 Station 200 in the oresent investigation was about 33 per cent saturated 



115 



