18 Farmers’ Bulletin 1185. 
is sometimes a part of the single-piece shell. Jor alfalfa spraying it 
should not have a central direct hole such as some orchard nozzles 
have. 
The rate of flow of a nozzle depends upon many details of size, 
shape, and design, but in nozzles of the same pattern it is governed 
by the size of the discharge opening and the pressure supplied by 
the pump. Thus a certain nozzle which is in common use, when 
provided with a five sixty-fourths-inch opening and a pressure of 125 
pounds, delivers a little more than four-fifths of a gallon per minute. 
For each additional 25 pounds of pressure the flow is increased one-. 
sixteenth gallon. The same nozzle with a six sixty-fourths-inch 
opening delivers as much liquid at 75 pounds as with a five sixty- 
fourths-inch opening at 150 pounds, and increases one-eighth gallon 
for each added 25 pounds. 
The discharge disk must be renewed occasionally, because the con- 
tinued friction of the liquid wears away the edges of the open- 
ing, enlarging it and increasing the rate’of discharge so that the 
material is wasted and eventually it becomes impossible to maintain 
the proper pressure. 
There is some difference of opinion as to whether the nozzles should 
point directly downward or slant backward. The writers have 
tried various angles and failed to find any advantage in one position 
over the others. 
The character of the spray produced by a plain nozzle of the 
type described in the foregoing paragraphs depends principally 
upon the pressure. With pressures below 75 pounds many of 
the particles of spray are so large that they roll down the 
surfaces of the foliage, collect in drops, and fall to the ground. 
At 75 pounds pressure the particles remain separate long enough 
to dry and form a fairly even coating, and as the pressure in- 
creases the spray becomes finer and the cover more nearly perfect. 
As the success of the work depends largely upon covering as nearly 
as possible all the upper foliage, the pressure should not fall below 75 
and might well be kept at 100 to 150 pounds. 
TOOLS. 
The tools needed in fitting up and using a spray outfit are, in 
addition to the usual hammers and wrenches, two 12-inch or 14-inch 
Stillson wrenches and a pair of pliers. The cutting and threading 
of the pipe used for the boom can be done at a plumber’s shop more 
economically than by buying the tools which would be required for 
doing the work at home. 
THE POISON. 
Arrangements should be made for obtaining the poison at the 
time when the machinery is being purchased or overhauled. Ar- 
