354 



of Horshor Island ; and declined again to about 3,500 at Al Fresco 

 Park. Mid-channel depths in the first two cross-sections were not 

 over 13 feet, but were 18 feet opposite Al Fresco Park, where the Icike 

 is beginning to taper to the lower narrows and the current is notice- 

 ably stronger than farther northward. Extra-channel depths in the 

 middle lake cross-sections were nearly all over seven feet, and depths 

 of nine to ten feet were met in all three throughout a total width sweep 

 of 2,500 to 3,000 feet. Soft mud bottom was found everywhere ex- 

 cept in the last hundred feet next the west bank, where there was some 

 sand or gravel. 



A more readily recognizable change for the better since 1 920 could 

 be perceived in the bottom sediments of the middle lake in the summer 

 of 1922 than was the case in the upper. Although bubbling was abun- 

 dant at nearly all stations, and mild bad odors at a majority of them, 

 no very foul odors such as were encountered in or near the channel 

 as far south as Al Fresco Park in 1920 were noticed anywhere in the 

 middle lake in the summer of 1922. Improvement between Mossville 

 and Al Fresco Park, a distance of about four and a half miles, was 

 clearly evidenced by the entire absence of foul odors and the fewness 

 of bubbles at a number of the wide-waters stations opposite the latter 

 place. 



Replacement of vegetation does not seem to have progressed so 

 far in the two years since 1920 in the middle as in the upper lake, a 

 circumstance possibly having some connection with the fact that the 

 middle lake is regularly seined. Sparse patches of Potamogeton and 

 Vallisneria were visible near the west bank in late August and early 

 September 1922 in the lower half of the lake, but the great weed-beds 

 that formerly covered hundreds of acres in the upper half of the lake 

 were as absent from the landscape as they were in 1920. 



Dissolved Oxygen 



There was a plentiful supply of dissolved oxygen over the greater 

 part of the middle lake in July 1922, when on gages between 11.3 

 and 10.7 feet more than five parts per million were -found a foot from 

 the bottom a mile below Mossville, and nearly or more than six parts 

 per million opposite Al Fresco Park in mid-channel samples. But 

 before the end of the first two weeks of .\ugust, on a gage down to 

 10,3 feet, the mid-chnnncl tigure a mile below ^lossville had dropped 



