LIMNOLOGICAL OBSERVATIONS IN THE UPPER MISSISSIPPI. 
371 
Table 10. — Sediment carried in various strata in Mississippi and Missouri Rivers. 
Locality and date. 
Parts of sediment in 1,000,000 parts 
of water. 
Surface. 
Mid depth. 
1 foot above 
bottom. 
Mississippi River (1880-81): 
Prescott 
123 
157 
159 
Winona 
34 
32 
36 
Clayton 
40 
42 
41 
Hannibal 
165 
208 
224 
St. Louis 
686 
906 
995 
Missouri River (1879): 
St.' Cliarles 
2,418 
2,473 
2,548 
CHEMICAL CONSTITUENTS OF WATER. 
The water of the Mississippi River is mainly a calcium carbonate water and 
is poor in chlorides and sulphates; the chlorides tend to accumulate in the lower 
stream. Table 11 gives the results of the chemical analyses of Mississippi water 
taken at Minneapolis and at Memphis. The figures are taken from Clarke’s work, 
“The Data of Geochemistry,” 1908. The data for Minneapolis represent an 
average of 23 samples, each formed by 10-day collections between September, 
1906, and May, 1907; those for Memphis represent an average of 17 10-day com- 
posites formed between October 29, 1906, and May 10, 1907. 
Table 11. — -Chemical analyses of Mississippi water at Minneapolis, Minn., and Memphis, Tenn. 
Ca. 
Salinity, 
CO,. 
SO,. 
Cl. 
NO,. 
Mg. 
Na, K. 
SiC>2. 
Fe20 3 . 
parts per 
million. 
Minneapolis 
47.04 
9.61 
0.85 
0.85 
20.59 
7.67 
5.33 
8.01 
0.05 
200 
Memphis 
32.02 
11. 31 
5.72 
0.10 
17.45 
6.98 
6. 19 
19.45 
.78 
197 
TRANSPARENCY OF WATER. 
The water of the Mississippi River is muddy even at its lowest stage; it is 
clearer in the upper part of the river and becomes more opaque down the stream. 
The transparency in the main channel above Lake Pepin is about 80 cm., in Lake 
Pepin it varies from 28 cm. at the shallow places to 102 cm. in the outlet, and 
in the river between Wabasha and Burlington it varies from 22 to 79 cm. The 
lowest transparency, 22 cm. (Station 18) for July and August, was observed at 
Fairport. . 
At the time of flood the river carries a great quantity of silt, and the turbidity 
of water increases with the rise of the stage. This was observed in September, 
when heavy showers caused a considerable rise of water in the letter part of the 
month. The rise started about the 16th and the water became very turbid, as 
shown in Table 12. 
The tributaries emptying into the Mississippi carry much sediment, and the 
transparency of their dirty, yellow water is sometimes only 2 cm. Observations 
made in the tributaries, most of them during the rise of the rivers when the tur- 
bidity of the water was greater than at low stages, are shown in Table 12. The 
amount of sediment in suspension in the mouth of Turkey River was as great as 
9 cm. 3 per liter, or 9,000 cm. 3 per cubic meter. The volume of plankton and 
detritus suspended at this time in the Mississippi water was about 20 cm. 3 per cubic 
meter. 
