24 BULLETIN 875, U. S. DEPARTMENT OF AGRICULTURE. 
ditches, etc., while driving. It must also afford sufficient rear illu- 
mination over the nozzles to enable the operator to make sure that 
the dust flow is regular. 
CAPACITY OF MACHINES FOR TREATING SEVERAL ROWS PER TRIP. 
In the earlier stages of the work it was attempted to make machines 
with adjustable nozzles that could be aimed directly at the rows 
being treated. It was soon found, however, that cotton rows vary so 
creatly in spacing that such an arrangement was impractical. 
Moreover, it was unnecessary. ‘The entire poisoning operation is 
based on the plan of creating a thick cloud of dust which will en- 
velop all parts of the cotton plants and coat them thoroughly. Con- 
sequently, all width-adjusting devices were eliminated and the noz- 
zles have since been spaced about 44 feet apart. ‘These nozzles are 
provided with deflecting plates or some similar spreading device 
which causes the dust clouds from the different nozzles to unite very 
quickly aiter leaving the machines, so that a uniform “ fog” ex- 
tending from row to row is created. Under such conditions it does 
not matter whether the nozzles are directly over the rows or between 
them. It has also been found possible under certain conditions to 
cover more rows than the nozzles actually span. This suggestion, 
however, should be taken very conservatively, as considerable ex- 
perience is required in the use of dusting machinery to determine 
just how far the drift can be considered as thoroughly effective in 
dusting. Until the operators have become thoroughly experienced 
in this work it is probably the best plan to figure on taking only as 
many rows as the distributor will actually span. 
FEATURES TO BE NOTED IN PURCHASING COTTON-DUSTING 
MACHINERY. 
For the benefit of those planning to purchase cotton-dusting ma- 
chinery, the following brief outlines have been prepared giving the 
inost important features which should be considered in order to make 
sure that the machines will be satisfactory. 
HAND GUN. 
The total weight should be not over 20 pounds when filled with 
poison dust. 
The hopper should hold about 4 to 7 pounds of calcium arsenate 
and it should be possible to put out practically all of this before 
refilling. 
The balance of the gun should be such as to cause the least strain 
‘on the operator, that is, the heavy parts of the machine should be as 
close to his body as possible. 
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