355 



to 2.2 p. p. m., and was only 3.4 p. p. m. a mile and a half above the 

 foot of the lake. Similar mid-channel figures (2.8 p. p. ni. one foot 

 from bottom) were obtained a mile below Mossville late in August 

 (gage 9.8 feet) ; and on September 13, after a slight rise, when the 

 low figure for 1922, 1.7 p. p. m., was recorded. At Al Fresco Park 

 on the last two dates mid-channel bottom oxygen was 5.3 and 4 p. p. ni. 



In the wide waters a mile below Mossville the bottom oxygen rose 

 rapidly toward the west bank in late July 1922, topping 10.2 p. p. m., 

 or about a part and a half above saturation, about a hundred feet from 

 shore on July 28. But in the far east wide-waters on the same date 

 the figures obtained a foot from the bottom ranged between 3.1 and 

 3.4 p. p. m., or a part to more than that lower than the channel figures. 

 However, at this time, in the wide waters as in the channel, bottom 

 oxygen figures rose rapidly as we proceeded down the lake, ranging 

 between four and six parts per million opposite the foot of Horshor 

 Island and six to more than seven opposite Al Fresco Park. On 

 August 9, 1922, bottom figures were under 1 p. p. m. in the open lake 

 at three stations in the cross-section a mile below Mossville, and were 

 as high as 3 p. p. m. only at distances more than 3,000 feet east or 

 2,000 west of mid-channel (it will be noted that the lake is some 2,000 

 feet wider at low water here than directly opposite Mossville). (Jn 

 the same date open lake figures opposite Al Fresco Park were under 

 4 p. p. m. as far as 1,300 feet east of the mid-channel line, but had 

 risen to 6.7 p. p. m. within a total of 2,000 feet. 



In August 1920 appreciably lower bottom dissolved oxygen figures 

 than any of those obtained in the summer of 1920 were recorded from 

 the middle lake, both in its upper portion in the vicinity of Mossville 

 and toward the lower end opposite Al Fresco Park. Then, as in 1922, 

 there was sometimes quite rapid improvement from the channel out- 

 ward into the wide waters, particularly in the lower portion. But in 

 the second week of August 1920, figures under 1 p. p. m. were found 

 more than 2,500 feet to the east of the mid-channel line at Al Fresco 

 Park. Neither in 1920 nor 1922 did these extreme low figures have a 

 very extended duration in the open lake, but were likely to be succeeded 

 within a week or two, coincidently with a sudden increase in the green 

 microplankton, by figures four to five parts per million higher. Even 

 bottom dissolved oxygen figures above saturation were recorded once 

 in 1920 from a middle lake wide-water station, late in August, though 



