486 



successive trips were made, the first from Lake Michigan and Lock- 

 port to Chillicothe, and the other two from Dresden Heights to tht 

 last-named point. Early autumnal conditions were studied from 

 Lockport to Chillicothe at various dates in September; late autumnal 

 conditions betw'^en the same points, November i-io; and winter 

 conditions at Mc.^ris and Marseilles, November 30 to December 3. 



On this last visit the collection of fishes from the more con- 

 taminated parts of the stream was first attempted by means of seines. 

 Observations on fishes had, however, been made at various points 

 from the beginning of operations in July. 



From the i6th to the 28th of February, 1912, efforts were per- 

 sistently repeated at Morris to obtain fishes from the river by the 

 use of seines and fyke-nets, and by the explosion of dynamite. Oxy- 

 gen determinations were secured at this time from all the usual 

 points between Lockport and Chillicothe, as well as from the Kan- 

 kakee above Dresden Heights; and the following month (March 18- 

 28) a full series of such determinations was made the whole length 

 of the river from Morris to Grafton, from the Des Plaines and the 

 sanitary canal at Lockport, and from the Mississippi above the mouth 

 of the Illinois. It was the object of this series to give us the data 

 for a comparison of extreme seasonal conditions throughout the 

 course of the stream. 



Lack of funds prevented a resumption of our biological river 

 work in the spring of 1912; but the new appropriations of the 

 Natural History Survey, available July i, fortified by an allowance 

 from the U. S. Bureau of Fisheries, enabled us to resume the collec- 

 tion of chemical and biological data August i, and to continue it 

 without intermission until October 25. 



In this time the chemistry and biology of the situation was stud- 

 ied, on two successive trips, at each point from Lockport to Chilli- 

 cothe, collections of plants and animals being obtained with dip-nets, 

 large and small seines, trammel-nets, set-nets, dredges, and the mussel- 

 bar, and by the explosion of half-pound cartridges of dynamite, and 

 oxvgen ratios being determined for each place and time at which the 

 biological data were obtained. 



Finally, in March, 191 3, samples of the bottom sediments were 

 collected from all the five Illinois River dams, and from some other 

 points in the main channel, for physical and chemical examination, 

 with a view to ascertaining the condition of the river bottom when 

 the river water has been for some months at or near the freezing 

 point. 



