or, for irrigating purposes, equal to a rainfall of over 1¼ 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 2½ 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 for each bucket, or 38 /
100 of a cubic foot.

The spill from this capacity of bucket being sufficient to compensate
for the friction of the shaft journals.

The lifting buckets of the noria class, Figs. 26 and 27, can be made of
positive dimensions to suit the computations as above; but those of the
tympanum class, Fig. 25, should be made of dimensions to conform with
the required capacity at the moment of leaving the water, as the water
at this point flows into the arm.

(_To be continued_.)