KEOKUK DAM 
97 
walls. Having passed these partial obstructions, it encounters the screens or gratings 
at the gates of the intake passages. The openings in the gratings (6 by 23 inches) 
are wide enough to admit most Mississippi River fishes but so close that a downward- 
moving fish probably would be deflected just as fish are deflected by the wide-meshed 
leads of a trap net. The investigators never saw a fish near the screens, except one 
or two that were put into the water for experimental purposes. The power com- 
pany’s guide, who walked by this head bay several times a day for nearly two years, 
stated that he never saw a fish here prior to April, 1915; on April 4 he said that a few 
days before he had seen four or five fish. Obviously, however, only surface-swimming 
fish would be observable, and it may be that such are deflected more than bottom 
fish by the ice fender and the arches of the foundations of the power house. 
A fish passing into the power house from above, through the screens, would 
nowhere find a narrower passage than the screen afforded, except in a single unit 
where the vanes admitting water from the scroll chamber to the turbine have an 
opening that is only about 5 inches wide, according to information supplied by the 
power company. Usually the opening between the vanes (fig. 13) is about 9 inches 
(23 centimeters). It may be remarked that the clearance between the vanes and the 
blades of the wheel is large enough to pass any fish of the locality. The blades 
or buckets of the wheel or turbine are 6 to 7 inches apart above, widening downward 
to 10 or 12 inches. It seems altogether likely that nearly any fish that passed the 
screens guarding the entrance above could continue with the current of water through 
the turbine chamber and draft tubes into the tailrace below. Experiments sub- 
sequently to be described (p. 112) show the possibility of their going through unharmed. 
LOCK 
The lock, which serves the uses of navigation, is between the power house and 
the dry dock. It is of particular interest, as it is the only passageway by which 
fish may go from the lower river to the upper, and it has been suggested that it 
might function as a fishway. The inside dimensions are 110 by 400 feet; the lift 
varies with the head, which is nearly the same as that on the turbines. The lower 
gates swing open while the upper gates submerge, working up and down in vertical 
slots. There are, in fact, two gates at the upper end — the ordinary “upper” gate, 
which is used regularly, and above this an emergency or guard gate, which is normally 
submerged. Water is admitted to and emptied from the lock through a series of 
culverts, the main running under the eastern wall of the lock, and having connections 
with both levels; either or both connections may be closed by valves. Branch 
culverts from the main run beneath the floor of the lock, and openings in these admit 
the water into the lock in a series of geysers, as shown in Figure 5, or permit it to run 
out when the upper valves are closed and the lower ones opened. 
It will be inferred from the description that fish would not be likely to enter the 
lock from below during the process of emptying, as to do so would be to pass through 
deeply submerging, sharp-angled tunnels, out of which the water is discharging at a 
velocity that is enormous until the lock is nearly empty. Likewise, they would not 
gain the upper lake from the lock during the process of filling at a corresponding 
velocity; furthermore, the intakes are screened by gratings, the openings of which 
are irregular in size, varying from 1/ to 2% inches. So far as it has been possible 
to learn by inquiry, no fish was ever seen to pass out here, and probably none ever has. 
