April, '11] worsham: spraying apparatus 195 



type of spray pump. When fitted out with good accessories they are 

 capable of spraying the largest fruit trees under ordinary conditions 

 and by far the larger part of all orchard spraying is done with pumps of 

 this class. Practically the same principles are incorporated in the 

 manufacture of the different makes, though the details of construction 

 vary greatly. 



It may be well in discussing this pump to consider what the essen- 

 tials of a good pump are. 



To begin with, it is necessary to have an air chamber to insure a 

 steady spray, otherwise the spray would be intermittent and pulsating. 

 The air chamber may be either separated from the working parts of 

 the pump or combined with them. In some styles it is on top of the 

 barrel, but in the-more satisfactory types it is within, and in the latter 

 the stability of the pump is greater. A large air chamber on the top 

 of the barrel renders it top heavy, and this top heaviness is likely to 

 be responsible for accidents when spraying on rough land. 



One feature of the barrel pump that is yet far from perfection is the 

 agitator. In most forms the paddle agitators are used, but these, while 

 they are all that could be desired for spraying materials free of solid 

 matter, will not and can not keep sprays such as the home-made lime 

 and sulphur thoroughly mixed. The tips of the paddles' describe an 

 arc of about 45° and work so slowly that the lime quickly settles to the 

 bottom with the result that the first part of the material as it comes 

 from the barrel carries much more free lime than the last, which has 

 but little. 



The question of the agitator for barrel pumps is an important one 

 and one that has not heretofore been satisfactorily solved. It is only 

 in gas power sprays that this feature is perfected. However, for the 

 materials now being used against scale insects which are uniform in 

 composition and carry no solids, an agitator is wholly unnecessary. 



The working parts of a pump, namely, the valves, valve seats, 

 plunger and cylinder, should be made of metal resistant to the corro- 

 sive action of the spray material. These are usually of brass, bronze, 

 or porcelain, substances not corroded by the action of the liquid. 



A pump should be compactly built with all the working parts closely 

 fitted so as to prevent leakage and attendant loss of power. All parts 

 should be easily removable for cleaning purposes and to make repairs. 

 Much trouble may be avoided by using only the best packing for the 

 plunger. The standard asbestos is far superior to leather or cord, 

 being more resistant to the caustic action of the spray and in every 

 way more durable and satisfactory. 



The spray pump market supplies a large number of different makes 

 of barrel pumps. Those best known to the author are the "Deming," 



