126 THE AMERICAN APPLE ORCHARD 



hand pump gives a very variable pressure on the liquid, 

 running from 125 pounds down to nothing, and seldom 

 averaging over 50 or 60 pounds. With any sort of 

 power sprayer, properly managed, a pressure of 100 

 pounds or upwards is easily maintained. With some 

 machines this pressure, say of 100 or 125 pounds, as 

 desired, can be kept up very steadily for hour after 

 hour, with practically no variation. In order to do any 

 sort of effective spraying a pressure of 65 pounds or 

 over is essential, about 100 pounds being the most 

 practicable figure. 



Traction Spray Machines A good example of the 

 first type of power sprayer, the traction machine, is 

 the Wallace pump. This machine takes its power 

 from the motion of the wagon wheel, which is pro- 

 vided with heavy lugs for that purpose, and is com- 

 municated to the pump by a sprocket chain and 

 wheels. While the wagon is in motion this power is 

 stored by compressing air into a large air chamber; 

 and this compressed air forces out the liquid for 

 several minutes after the wagon stops. The air 

 chamber and the pumps are connected with a bar- 

 rel mounted on the same truck; or better still the 

 whole machine is mounted on a large special tank 

 holding 200 or 300 gallons of mixture. 



In our experience it is not practicable to operate a 

 traction sprayer at a pressure of more than about 80 

 pounds. This pressure goes down slowly as soon as 

 the wagon stops, but will not go below 65 pounds in 

 less than 2 or 3 minutes in operating two gangs of 

 vermorel nozzles. In young orchards where the trees 

 are small, and on comparatively level land, and where 

 the most thorough spraying is not required, the trac- 

 tion machines seem to be worth while. When any one 



