Spraying Devices and Machinery. 211 



or the chamber could be completely filled. Different styles of 

 nozzles were used with the varying capacity of the air cham- 

 bers, so that the experiments might be as conclusive as possible. 

 A sensitive steam gauge was also attached so that the pressure 

 could be measured. 



The results showed that no greater force could be obtained 

 whether a large or a small air space was present ; the pump 

 did riot appear to work more easily with a large chamber than 

 with a small one, nor did the character of the spray appear to 

 be modified. A great difference could be seen, however, in the 

 length of time required for a nozzle to throw its best form of 

 spray, since the character of the spray of most nozzles varies 

 with the pressure of the liquid. It was also noticed that the 

 flow of liquid continued much longer when a large air chamber 

 was attached, but as the pressure decreased, the value of the 

 spray decreased, so that only the main flow was suitable for 

 making applications. As many nozzles are not provided with a 

 stopcock for shutting off the flow of liquid, there is more or less 

 loss of material whenever the pumping ceases. There is also 

 a loss of time and material when the pressure is increased, since 

 the flow from the nozzle is delayed as the capacity of the air 

 chamber increases. The work indicated that for all practical 

 purposes an air chamber having a capacity of one pint to one 

 quart is sufficient for any barrel pump or for any nozzle. It 

 allows a quick application of pressure, and its almost immediate 

 removal, while the air cushion is sufficiently large to produce a 

 uniform spray. 



The agitation of most of the liquid insecticides and fungi- 

 cides is, unfortunately, necessary; otherwise the undissolved 

 particles settle at the bottom of the tank, and, in consequence, 

 the applications are uneven. Even a knapsack pump will not 

 maintain proper agitation, although it is thoroughly shaken by 

 the man carrying it. Some certain means of agitating the 

 liquid must, therefore, be adopted. Attempts have been made 

 to force a return stream of the liquid into the barrel or tank, 

 and the currents so produced were supposed to answer the 

 desired purpose (see Fig. 28). But the results have not shown 

 this to be the case, and this class of agitators is being gradu- 

 ally abandoned. Another, and more effective, method is to 

 attach a paddle or dasher to the handle or other moving part of 



