330 



record or records of uncertain value at seven stations. This exhibit 

 compares with bad odors at all stations in the summer of 1!)20, but is 

 qualified in value by the feature that worse odors were noted in the 

 summer of 1922 well to the east and west of the main channel than 

 within it. both opposite Rome and just above Spring Bay ; and rather 

 milder ones in the river channel at Chillicothe than at the worst sta- 

 tions in the wide-water cross-sections three to five miles farther south. 

 The possibility that the very unusual flood of January-April 1922 

 flushed out the channel at the same time that it brought in a new load 

 of putrescible sediment to the wide waters suggests itself as a plau- 

 sible explanation of some of these changes, as also of the fact that the 

 spongy gas-filled mud noted in the summer of 1920 at several upper 

 lake stations in or near the steamboat channel did not appear in any of 

 our 1922 dredge hauls. 



Toward the west bank below Rome some spreading of Potamoge- 

 ton occurred between 1920 and 1922 ; and in September 1922 mats of 

 Lemnaceae were found here, and also in the brushy southwest corner 

 of the upper lake opposite Spring Bay. The total area supplied with 

 vegetation is, however, insignificant compared with that of the low- 

 water period between 1910 and 1915, on gages little if any lower. No 

 living vegetation at all was encountered at any of tiic stations actually 

 dredged in the summer of 1922. 



Dissolved Oxygen 



The dissolved oxygen one foot from the bottom in mid-channel 

 at Chillicothe fell as low as 0.3 p. p. m. in July 1922, and to 0.2 p. p. m. 

 in August. The bottom oxygen during the same period in mid-channel 

 opposite Rome dropped to 0.2 p. p. m. on July 3, 1922 ; rose to 2.0 

 p. p. m. on July 27; fell to 0.5 on August 9; and rose again to 1.G on 

 August 29. On August 9, when the bottom oxygen in the channel at 

 Rome was 0.5 p. p. m., bottom figures under one part per million were 

 recorded at six wide-water stations east of the steamboat channel in 

 the Rome cross-section, averaging more than 600 feet apart and ex- 

 tending altogether more than 3600 feet eastward of the mid-channel 

 station. 



At points between a mile and a half above Spring Bay and the 

 foot of the upper lake at Spring Bay Narrows, which is 7.7 miles be- 

 low Chillicothe. the bottom dissolved oxygen in July and .lugiist 1922 



