358 Report of the Horticultural Department of the 



and of agitating require very different kinds of strokes to get the best 

 results. Pumping requires a slow, steady stroke, while a quick^ 

 sharp motion is best for agitation. The fact of being independent 

 also permits of agitation before pumping begins, a time when the 

 spray mixture is especially liable to be lacking in uniformity. This 

 is not practicable in most outfits in which agitators and pump are 

 actuated by a common lever. But in a few cases the plunger of the 

 pump can be readily detached from the lever by simply withdraw- 

 ing a pin. and the mixture can receive a preliminary agitation. In 

 the case of jet agitators of course the preliminary agitation can be 

 given by pumping back into the tank. 



Jet agitators. — Jet agitators operate by returning a small stream 

 of liquid under pressure from the pump to the bottom of the tank. 

 Two are shown in Figs. 19 and 24. Jet agitators have been almost 

 wholly discarded in practical work with hand pumps because it is 

 impossible in pumping by hand to keep up pressure enough to sup- 

 port the best kind of a spray even when none of it is used for return- 

 ing a stream into the tank. While jet agitators in general as used 

 in hand outfits, rank below the mechanical agitators in efficiency, as 

 used in power outfits with excess of power they may be made very 

 efficient. With them it is possible to agitate the liquid before spray- 

 ing begins, which is a decided advantage. ^Moreover, when made of 

 brass they do not offer a surface on which sediment can collect, to dry 

 when the tank is not in use and to scale off later with resulting lia- 

 bility to clog the nozzles. 



EXTENSION RODS. 



Extension rods are used in connection with discharge hose for such 

 purposes as reaching the higher branches of trees. By their use the 

 spray can be put where wanted, whether into the interior of the tree 

 or on the outermost branches. 



Extension rods are of two kinds, pipes supported by a rod of wood 

 and pipes with no support. The former usually consist of a length of 



