Pumps and Nozzles 



327 



which the liquid is whirled, and it is then projected through 

 a disc with openings of different sizes. The bordeaux 

 nozzle is also used for the codlin-moth and some other 

 purposes. The spray liquid should penetrate the top of the 

 tree and drench all the leaves; this requires not only a 

 good nozzle but much force, more than the usual hand- 

 pump develops. 



Remarks similar to the above may be made for pumps; 

 that is, there is no one best pump. We might divide all 

 pumps into two general classes, those that deliver the 

 liquid by force of gravity, as some of 

 the potato sprayers, and those that 

 deliver it by the force of pressure. The 

 force of gravity is not 

 sufficient to do the work 

 well, especially when bor- 

 deaux mixture is to be 

 used. Of the pressure 

 machines, there are sev- 

 eral kinds, as those that 

 derive their force from the 

 suction of a piston and 

 valves, and those that work from the force of compressed 

 gas or air. Knapsack pumps are very efficient, not only be- 

 cause they are powerful for their size, but also because they 

 enable the operator to stand very close to his work; but 

 they are not adapted to work on trees nor, in fact, on large 

 areas in this country, because labor is too high-priced. 

 For small areas, for experiment purposes and the like, they 

 are exceedingly useful and handy. The syringe and bucket 

 pumps are very efficient for work in, a small way in yards, 

 and especially when it is desired to be extra thorough. 



The force or power to drive a pump may be the arm 



FIG. 123. Platform above a tank outfit. 



