514 



month, although they were abundant in Mazon Creek, and in the 

 slough at its mouth, which opens into the Illinois at Morris. Carp 

 were noticeably numerous in this slough, and could be seen any 

 sunny morning lined up along the edge of the river current, oc- 

 casionally venturing into it a short distance, but quickly returning. 

 After August lo, when rains brought the river up about six inches, 

 the carp began to come out of the slough into the river along the 

 south bank. 



Late Snnuncr and AutiDun Conditions, igii. — Towards the end 

 of July, cooler weather and higher water produced changes which 

 presently had their effect on the life of the river. The midstream 

 temperature was 6.7° F. cooler on the 28th of July than it had been 

 on the 22d, and a heavy rain August 10 — the first excepting one 

 light shower since our operations began, July 15 — brought the river 

 up about six inches. The fall rains began about the middle of 

 September, and the river rose until, by October 5, it was four to five 

 feet above the mid-July level. It then fell slowly about three feet 

 in October, was brought up again a foot by November 11, and by 

 the end of that month had declined to two and a half feet above the 

 July stage. Water temperatures in the midstream ranged from 63° 

 to 72° F. in August and September, and by November 3 (at 9 a. m.) 

 were down to 41°. The midstream oxygen ratios of this late summer 

 and autumn season averaged 1.44 parts per million in August, and 

 stood November 3 at 4.55, or 16.5 per cent, of saturation for August 

 and 41.3 per cent, at the beginning of November. 



Reappearance of Fishes and other Animals. — By October, fishes 

 had begun to appear to some extent in the river, even along the 

 northern or contaminate side, where a few young perch, shiners 

 (Notropis atherinoides), straw-colored minnows (A'', blennius), and 

 a single top-minnow {Fundnlus notatns), were taken in places pro- 

 tected from the strong current. Shiners and straw-colored minnows 

 were seen again in the same situations November 3, and carp were 

 occasionally noticed on the south side of the river during the latter 

 part of October. December 2, the first systematic attempt to take 

 fishes at Morris was made, by hauling repeatedly a hundred-and- 

 twenty-foot minnow seine in slack water along the north bank. Al- 

 though weeds and sticks were slimy with Sphcerotilits natans and 

 Carchesium lachmanni, which were also floating in the shallows, 

 numbers of young perch three to six inches long were captured here, 

 together with many shiners — two to four inches^ — and a single black 

 bullhead {Ameiurus nielas), three inches long. An examination of 

 the stomachs of these specimens showed that none of them had 



