118 
BULLETIN OF THE BUREAU OF FISHERIES 
VELOCITY OF CURRENT 
The rate of the current on the old rapids is given in a report to the Secretary 
of War (Hains, 1867, p. 277), as follows: “Its mean surface velocity is 2.88 feet per 
second, and its mean velocity deduced therefrom is 2.304 feet per second” (a little 
more than 1 ){ miles per hour). A study of the former current at Burlington was made 
with much refinement by Mackenzie (1884) in the month of October. He found it 
to vary from 1.2 feet per second (0.82 m. p. h.) on October 7 at a depth of 16 feet 
to 2.9 feet per second (1.98 m. p. h.) on October 14 at a depth of 1.7 feet. Doolittle 
(MS.), in the summer of 1914, made three observations each near Keokuk and 
Nauvoo and two near Burlington; these were presumably at or near the surface. 
Table 7, based upon these records, shows roughly the difference between the old 
and the new conditions. At Burlington the current has been scarcely checked; 
right above the dam it has been almost stopped. The velocity on the old rapids 
must have been much greater at times than these figures show. In 1910 (Franken- 
field, 1911, p. 234) the stage at Galland rose 3.9 feet (1.2 meters) from December 
21 to 22 and had fallen 4.3 feet (1.3 meters) the next day. On the second of these 
two days the velocity at and below Galland must have been very great. 
Table 5. — Velocity of former river, in miles per hour, compared with present lake 
Place 
Old river 
Present 
lake 
1. 58 
0. 0-0. 4 
Nauvoo, 111., 12 miles north of dam 
. 64-1. 2 
Burlington, Iowa, now the upper end of lake 
0. 82-2. 0 
1. 13-1. 8 
BOTTOM MATERIAL 
The bed of the old rapids was described by Hains (1867, p. 277) as “a broad, 
smooth rock, seamed by a narrow, crooked channel, or in some places several of them, 
alternately widening and narrowing, shoaling and deepening * * *. The rapids 
are, therefore, not broken and noisy, but, the descent being gradual, the water flows 
over its bed in a broad, smooth, unbroken sheet, with nothing but the faintest ripples 
on its surface * * *.” Keys (1895, p. 316) states that the bed of the rapids was 
chert (a quartz similar to feldspar) lying at the top of the Burlington limestone. 
Charts Nos. 136 to 140 of the survey by the Mississippi River Commission show 
patches of sand and gravel at the upper end of the rapids; from here to Burlington 
the bottom was nearly all sand, with some rock and gravel and scarcely any mud. 
Writing of the conditions in 1914, Doolittle (MS.) states that the bottom of the lake 
where sounded or dragged was a fine bluish-gray mud, but that a sand bar had formed 
off Nauvoo, 111. On July 4, 1917, many soundings were made within about one- 
half mile above the dam, and only mud was found, except close to the banks. Refer- 
ence may be made here to the remarks concerning the silting in of the area of the former 
rapids, made in the section of the companion report (Coker, 1930) entitled “Fresh- 
water mussels.” 
PLANKTON OF THE LAKE IN 1914 
In the second season of the lake, Dr. A. A. Doolittle made for the bureau a series 
of studies of the plankton of Lake Keokuk. It was expected that the survey would 
be repeated after the lake had aged two or three years, and that the results of the two 
surveys in comparative form would be prepared for publication. Doctor Doolittle 
