Spraying for the Alfalfa Weevil. 13 
For a permanent structure a frame of 4 by 6 inch timber may be 
fitted to the wagon and a 200-gallon tank mounted with the other 
machinery upon it. The most convenient homemade truck is a flat 
rack. Commercial orchard spray trucks, usually furnished with low 
wheels and broad tires, may be used, but high wheels are better for 
spraying tall alfalfa, not because they break down less alfalfa, since 
this is only temporary, but because they make it easier to attach the 
spray boom at the proper height, and cause less jolting of the 
machinery in driving over rough ground. 
THE TANK. 
Commercial spray tanks are usually in the form of a half cylinder, 
made of redwood, cypress, or steel, with a capacity of 200 gallons. 
. Homemade tanks are usually 50-gallon barrels, four of which, with 
an engine and pump, can be carried on an ordinary wagon or a flat 
rack. Two hundred gallons of water is load enough for a team in 
most fields. If the water has to be hauled a long distance a second 
team and a thrasher tank should be used for that purpose instead of 
the spray outfit. | 
The most important item connected with the tank is the agitater. 
Since the poison is not dissolved in the water, but merely mixed with 
it, it will gradually settle to the bottom of the tank, leaving only a 
weak mixture to be applied to the plants, unless the liquid is stirred 
constantly and vigorously. For this purpose commercial outfits use 
a paddle or propeller within the tank, operated by a shaft, sprockets, 
belt, or drive rod from the pump or jack. In barrels the liquid can 
be stirred by a paddle or dasher worked by the jack or pump or by 
hand. -— 
A strainer of 20-mesh brass or bronze screen should be fitted over 
the opening through which the water enters the tank and another 
over the outlet from it which leads to the pump. The former may 
be at the end of the suction hose, if one is used for filling the tank. 
If a cloth cover is used to keep the tank or barrels from slopping 
over it should be of canvas rather than burlap or any other linty 
fabric. 
THE PUMP. 
In spray pumps of all sizes certain structural features are im- 
portant because of the corrosive nature of the liquid and the need 
of a uniform flow at comparatively high pressure. 
The cylinder lining, plunger, valves, valve seats, and other working 
parts in which a close fit is required, and which also come in contact 
with the arsenic, must be of brass, bronze, porcelain, or some other 
substance which is less rapidly corroded by the chemicals than are 
iron and steel. To maintain the pressure without waste of power 
