No. 6. 



DEPARTMENT OF AGRICULTURE. 



503 



SO used. The agitators now in common use are far from perfect 

 and unless carefully watched are often the cause of failures. It has 

 now come to be almost the universal custom to attach the agitating 

 device to the pump handle, so that the liquid is stirred with every 

 stroke of the operator. This at first sight seems a good plan. In 

 some respects it i», for it at least secures some sort of agitation, 

 which is better than none at all. But the labor of pumping, so as to 

 keep the pressure up to the required mark, is really heavy enough 

 without adding to it the extra work of keej^ing a properly con- 

 structed agitator at work. Then, too, the two motions can hardly 

 be coupled to advantage. For the pumping, a long, steady stroke 

 is best, while for thorough agitation a quick, abrupt stroke is prefer- 

 able. It is very much better, therefore, to have the agitating device 

 separate from the pump. In this way a few vigorous strokes or 

 tUT.s of the liaudle accomplish a great deal better work than the 

 slow dipping of a paddle. Agitators having a whirling paddle with 

 tilting blades arranged somewhat like a screw propeller are, on the 

 whole, the most satisfactory. (Fig. 3.) With this instrument the 



liquid is given a whirling up- 

 ward motion, w^hich very ef- 

 fectively dislodges the ma- 

 terial from the bottom and 

 sides of the tank. On the 

 long, flat tanks now in gen- 

 eral use it is practically im- 

 possible to secure thorough 

 agitation throughout the 

 liquid by any device which 

 may be attached to the pump 

 handle. For these tanks the 

 agitator should consist of a 

 set of two or three paddles so 

 arranged that they will keep 

 the whole body of liquid in 

 violent motion. These pad- 

 dles should be attached to a 

 lever or handle on top of the 

 'FIG. 3. tank. Where Paris green is 



used alone, the agitation must be continuous while the pumping 

 is going on, and in order to insure its thoroughness it would pay to 

 put on an extra man or boy to run the agitator. With properly 

 prepared Bordeaux mixture (as will be explained later) continu- 

 ous agitation is unnecessary. Merely stirring the liquid from time to 



