Spraying Devices and Machinery. 217 



ideal spray pump. Yet the manufacturers have admitted that 

 these pumps are not so durable as the other styles, and 

 this necessarily follows from the manner of their construction, 



FIG. 31. Semi-rotary or " clock " pump. 



They are also more delicate, and will not bear the abuse which 

 appears to have no effect upon other forms. When clear solu- 

 tions are applied there is little to wear the inner parts, but with 

 gritty preparations, such as the Bordeaux mixture, their days of 

 service are not very long. 



