234 
cycles of limnetic organisms at this middle reach of the river 
comes accordingly to depend to a great extent, not upon 
the primary contributions of the sewage, but upon secondary 
or even later conversions of the nitrogenous matters originally 
contributed. The decay of the vegetation of the backwaters 
and bottom-lands, and the wastes and decay of the plankton 
itself and of the other organisms dependent upon it, come to 
be to a greater extent the immediate sources of support of the 
locally developed plankton. 
COMPLETE MINERAL ANALYSES. 
Three complete mineral analyses of the water of the 
Illinois River have been made by the Chemical Survey under 
the direction of Professor Palmer, the samples for which were 
collected by us at Havana. These appear in the accompany- 
ing table. 
ANALYSES OF MINERAL MATTERS CONTAINED IN SAMPLES COLLECTED FROM 
ILLINOIS RIVER AT HAVANA, ILLINOIS. PARTS PER MILLION. 
\Nov. 1and2,| Oct. 31 and | Junets, 
| 1897 Nov. 1, 1898 1900 
ICrilel Eee oo ne cere dae AGS Ga OuAb Eta nas 0.0 trace 0.0 
Potassium phosphate K3PO............. 0.0 2.4 0.0 
Potassium nitrate KINO seas essere 5.05 2.4 6. 
Potassium nitrite INO? as usenicnine 6.06 0.0 0.0 
Potassium chloride KiGwe tensa tanewe 3.72 4.4 2.2 
Sodium chloride NaGivecey nace 100,85 44.2 21.4 
Sodium sulphate Na2SO,4.........-- 17.72 27.5 20.1 
Ammonium sulphate (NH4)25O4........ 6.21 10.2 2.2 
Magnesium sulphate IMB SO per ticetaves 31.02 33-4 35-5 
Magnesium carbonate MgCOs........... 74.01 Cir fes} 69.7 
Calcium carbonate CaGO sts ose minocte 137-79 150.3 267.5 
Iron carbonate HeCOsrecenieecen 3.2 3 6.6 
Alumina Alla@syis2 i slerneyrrels 8.95 ey, Ife 
Manganese oxide MnO 5 ive scwicistetieiers 0.0 0.0 0.7 
Silica SiOs sees neceee 26.07 31.6 27.6 
BING EAN ets tstatel ajcie ae etsssyershermraneistaysteaetetatenetenee 420.65 385.7 466.5 
The analysis in 1897 was made in a period of prolonged 
low water, the effect of which appears in the large amount of 
sodium chloride, indicating the concentration of sewage, while 
the presence of potassium nitrite suggests the active decay of 
