242 
Journal of Agricultural Research 
Vol. XXXI, No. 3 
ditions ascertained. The brake-horsepower curve does not start at 
zero as do the capacity-head and efficiency curves, as indicated in 
Figure 9. For zero flow, the power consumed amounted to 9.48 
horsepower, and the pump speed was 912 revolutions per minute, 
although the pump did no useful work. The curve reaches a maxi¬ 
mum at 34.3 horsepower, with a total head of 56.3 feet and a flow 
of 1,130 gallons per minute. At the point of maximum capacity, 
the power output has decreased to approximately 33.7 horsepower 
and 39 feet head. This is a very important factor in connection 
with tests, as it shows that with a prime mover of 35 horsepower 
overload conditions would never exist at this speed, viz, 898 revolu¬ 
tions per minute. If the speed of the pump were increased as shown 
in Table I, new limits of capacity would exist. In any case, the 
pump should be operated so as to give an efficiency in excess of 50 
per cent. 
SPEED CURVE 
The speed curve is the indicator of the proper speed at which to 
operate the pump to give best efficiency for a given head and capacity. 
This is a detail, already pointed out in this report, which must not 
