n construction.

We illustrate the most simple of these forms in Figs. 26 and 27, in
which the first is a series of boxes or chambers in the rim of the wheel
with side openings in the forward part of the box as the wheel revolves,
and a lip extending from the inner edge of the opening to direct the
outflow into the trough.

[Illustration: Fig. 26.]

Another form, Fig. 27, is arranged with swing buckets or pots, pivoted
just above their centers, and with the catch trough so fixed as to tip
the buckets at the highest point, thus giving this wheel the greatest
possible advantage as to height of discharge for a given diameter.

[Illustration: Fig. 27.]

The power value of these wheels for raising water is a matter of
computation as nearly reliable as for other devices for the same
purpose, when the velocity of the current is known at the point of
contact with the blades.

The horse power of the wheel may be computed as for the current wheel,
Fig. 23, and, as the horse power is equal to 33,000 pounds raised one
foot high per minute, we may assume a construction of wheel that will
allow of discharging at 8 feet above the stream; then 33,000 / 8 = 4,125
pounds of water discharged at 8 feet elevation per horse power per
minute. As the net power of the wheel in the last example, for Fig. 23,
was 0.468 of a horse power, then 4,125 x 0.468 = 1,930 pounds of water
raised 8 ft. per minute by the size of bucket and velocity of current in
that case. From this a deduction of 20 per cent. should be made for loss
by spill and imperfect construction, so that 1,500 pounds or 176 gallons
per minute would be the probable output--over 253,000 gallons per day;
or, for irrigating purposes, equal to a rainfall of over 11/4 inches in
depth on 50 acres in one week.

The proportion of capacity of the lifting buckets for such a wheel
becomes of as great importance as its efficiency.

If the buckets are too large, the wheel will stall, and if too small,
the wheel will not give its full duty.

For obtaining the approximate capacity of the lifting buckets, assuming
the example as above computed, a 10 foot wheel with the velocity at
periphery of 21/2 feet per second is 150 feet per minute, or five
revolutions per minute, nearly. Then 1,930 lb. per m. / 5 revolutions =
386 pounds water capacity for all of the buckets on the wheel.

If such a wheel is constructed with 16 blades and 16 buckets, one
between each blade, then 386 / 16 = 24 pounds