SPRAY PUMPS 



181 



in a large chamber. This compressed air, in turn, forces the 

 liquid out of the tank. The great objection to this machine is 

 that the pressure runs down as soon as the wagon stops. And 

 since it is absolutely necessary to stop in order to do good 

 spraying on trees of any size the best orchardists have ruled 

 this machine out of their list. It is all right with small trees 

 where the outfit travels a considerable distance for every gallon 



FIG. 81. Gas power sprayer. An excellent type in some respects, but it is too difficult to 



clean out the tank. 



of liquid put out, but most orchardists cannot afford so expensive 

 an outfit for this one type of spraying. 



In the second place, there is the gas sprayer, shown in Figure 

 81. This consists of an air-tight steel tank which holds the spray 

 material, and a tube containing carbonic acid gas under pressure. 

 The tube of gas is connected by suitable pipes and valves with 

 the tank of liquid and when one is ready to spray he simply turns 

 the valves and lets the gas into the tank. This, of course, 

 exerts a pressure on the liquid and it is forced out through the 

 hose. In some respects this outfit is admirable. It is relatively 



