SPRAY PUMPS 179 



2. It ought to have a good-sized air-chamber. This does 

 not mean that the air-chamber should be conspicuously placed 

 on top of the pump as is often the case. It can be as low down 

 as desired, but it will keep the pressure much more uniform. 



3. There should be as few and as small openings about the 

 pump as is compatible with the free working of the plunger and 

 agitator. The splashing of the liquid through these openings 

 is bad enough at best; a prize awaits the manufacturer who 

 develops a pump which does not splash the operator. 



4. The pump ought to have a good agitator. As already 

 suggested, most of our spray materials carry more or less solid 

 material in suspension, and these ought to be distributed evenly 

 with the liquid. With an inefficient agitator the operator gets 

 nearly all the poison on the first few trees and the balance are 

 sprayed with plain water, or nearly so. 



5. There ought to be a good strainer at the bottom of the 

 pump. Even with the most careful preparation of the materials 

 and the most thorough straining there is always danger of some- 

 thing getting into the pump that will clog the nozzle. The 

 strainer is an additional safeguard. If it can be such as can 

 be readily taken off and cleaned so much the better. And if 

 the actual straining area is on the bottom instead of on the 

 sides of this strainer it will come nearer to emptying the cask. 



6. The pump should have all brass working parts. In these 

 days of strong corrosive materials the best of pumps will wear 

 out soon enough. 



7. The valves should be simple and easily accessible. It is 

 astonishing how often a valve will get stuck, even when the 

 pump receives reasonably good care. The operator should know 

 just where it is and how to get at it and the manufacturer should 

 put no unnecessary difficulties in the way. 



8. The type of packing ought to be simple and the method of 

 renewing it or of tightening it should be easy. This is an 

 extremely important point. The packing is bound to wear and 

 allow leakage, and no one wants to be obliged to resort to a 

 machinist or a high-priced (and low-speed) plumber to get his 

 pump fixed. 



