Spraying 



pumped in so as to get a pressure of 100-120 lb. to 

 the square inch upon the liquid in the container 

 before spraying is commenced. Both types of 

 machine are good, but with the pneumatic type 

 there is some danger of attempting to spray with 

 too little pressure, and there is also the need for 

 testing occasionally to ascertain that the machine 

 is sufficiently strong to withstand the necessary 

 pressure. 



In any case the container should hold from three 

 to three and a half gallons of spray, and the machine 

 when charged should weigh about 40 lb. The 

 contaiaer may be made of copper unless Ume- 

 sulphur is used, when it must be made of some 

 other metal not liable to be attacked by this com- 

 pound. It should be of a form to fit comfortably 

 upon the back, and have broad shoulder-straps of 

 such a length that the loaded machine will ride easily. 

 If of the continuous pumping type the pump handle 

 should come conveniently to the hand. In both 

 types all parts at all likely to get out of order should 

 be easily reached for adjustment ; the valves are 

 best of metal and the washers of leather. Leather 

 is generally preferable to rubber, for the latter is 

 more apt to perish. A supply of washers and spare 

 wearing parts should always be near at hand. 



Means should be provided for ensuring that the 

 spray fluid is kept in a state of agitation during 

 spraying. This is less important when the machine 



145 L 



