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 

 greatly 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 4-| 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 after 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 

 most 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. 



