[Illustration: FIG. 32.--TURBINE WHEELS; INFLOW TYPE SHOWN ON THE LEFT AND OUTFLOW TYPE ON THE RIGHT]
The turbines used at the Keokuk plant are of the inflow type. The rotor is mounted on a vertical shaft in a scroll-shaped concrete chamber, something like a snail shell. Water pouring into this chamber is thus given a swirling motion in the direction of rotation of the wheel. As it flows into the wheel it passes first through a ring of fixed vanes, which divide it into the jets.
The highest velocity of a wheel is naturally at the periphery and the advantage of an inflowing turbine such as this is that the water is traveling at its highest velocity when it strikes the periphery of the rotor. As it loses its velocity it flows in toward the slower-moving portions of the rotor. Finally it reaches the center, after giving up practically all its energy, and falls into the tail pool through a draft tube at the center of the rotor.
The scroll chambers at Keokuk are thirty-nine feet in diameter and the draft tubes are eighteen feet in diameter. Water enters the scroll chambers with a velocity of fourteen feet per second and comes out of the draft tubes into the tail pool with its velocity cut down to but four feet per second. Compare this with the velocity of the water jets at Big Creek!
The current generated at Keokuk goes to St. Louis and surrounding towns and serves a population of 1,120,000.
Now that we have learned how to transmit electrical power without serious loss over enormous distances, it is only a question of time before all the water power in the world is harnessed and put to the service of man. The power costs nothing after once the plant has been built; the only expense is that of maintaining the machinery and keeping it in repair. It is estimated that there is some 200,000,000 horsepower available in this country, but this includes all flowing water, much of which it would be impracticable, if not almost impossible, to utilize. However, there is about 60,000,000 horsepower commercially available, according to the figures of the U. S. Geological Survey, of which we have developed so far only 6,000,000 horsepower.
The ancients used flowing streams not so much for power purposes as to lift water to a higher level so that it would flow into their irrigating ditches. Nowadays, electricity, steam, or air is used for elevating water, but we have a very ingenious machine which makes the stream lift a part of itself. This machine is very different in principle from the old Egyptian noria. It depends upon the kinetic energy of water in motion. You cannot push a nail into a piece of wood with a hammer but you can easily drive it in by striking it with the hammer. As the hammer is swung it acquires what we term kinetic energy or energy of motion.