10 Farmers’ Bulletin 1185. 
taking up the various items in an order nearly the reverse of that 
in which they have just been mentioned. The best results have 
been obtained with nozzles working 2 feet above the alfalfa, each 
aozzle as it moves across the field spraying a strip 2 feet wide. A 
single nozzle in spraying an acre, which is 43,560 square feet, there- 
fore covers a strip 2 feet wide and 21,780 feet long, or, in other 
words, travels 21,780 feet. It is now considered desirable to apply 
100 gallons per acre, and in order to do so the nozzle must deliver 
1/21,780 of that quantity to each linear foot of the strip; and as 
200 feet per minute is an average walking gait for a team hauling 
the outfit, the nozzle must deliver 200/21,780 of 100 gallons, or 0.9° 
of a gallon per minute. 
The same figures show that the time required to spray an acre 
with one nozzle is 21,780-—200, or 109 minutes. If twice as many 
nozzles are used the strip sprayed will be twice as wide and one-half 
as long, and the time required will be one-half as great; and so the 
time and the amount of driving required will vary as the number 
of nozzles is increased, but the rate of flow of each nozzle must be 
kept the same so long as the driving gait and the quantity per acre 
are unchanged. 
Knowing the number of gallons with which each nozzle must be 
supphed per minute it is easy to compute the capacity required of 
the pump for a given number of nozzles, or the number of nozzles 
which a given pump will support. It is also possible to calculate 
how large an outfit will be needed to spray a given area in a given 
time, or how large an area a pump already on hand can spray in a 
given time, according as the controlling factor is the kind of pump 
which is available, the number of acres which must. be sprayed, or 
the time which can be devoted to it. Thus 10 nozzles, each dis- 
charging 0.9 of a gallon per minute, will require a pump which can 
deliver 9 gallons in that time, and such an outfit will spray an acre 
in about 11 minutes of actual work. Such a machine is shown in 
figure 7. : 
The capacity of a pump depends upon the size of the plunger, 
the length of its stroke, and the number of strokes per minute, and 
can therefore be ascertained by a simple calculation. The area of 
the piunger is found by dividing its diameter, in inches, by 2, 
multiplying the result by itself, and that result again by 3.1416. 
This result, multiplied by the length of the stroke in inches, gives 
the contents of the cylinder in cubic inches, which is reduced to 
gallons by dividing by 231, and gives the quantity delivered by a 
stroke of the pump. If the latter is double-acting, as most of the 
better spray pumps are, this must be multiplied by 2. The delivery 
per minute is then obtained by multiplying the number of gallons 
per stroke by the number of strokes per minute. 
