236 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 



may be made as usual. This on tbe excurrent orifice may be through 

 either head of the bellows, the latter preferably toward the poison res- 

 ervoir. Across either head may be added a cleat, which also can be 

 hollow, with a discharge or suction passage, and may extend beyond the 

 bellows as a spout or handle. A reacting spring to expand or open the 

 bellows can be placed inside, or else outside betw^een the projecting ends 

 of the cleats, spouts, or handles. Some varieties of these bellows, 

 methods of operating them, and ways in which they are susceptible of 

 being combined with nozzles, reservoirs, &c., will be particularly noticed 

 in the special apparatuses to be described. 



Oscillating Blowers of Powder.— Instead of the various hop- 

 pers, which generally allow the poison to escape beneath the cover, or 

 permit moisture to enter there when the plants are wet or in case of 

 rain, it is better to employ a water-tight can, closed by a large can-screw 

 cap or plug. The can may be of any convenient size or shape, and 

 any other ordinary reservoir, as a tight keg or barrel with a large bung, 

 can be used in its stead. 



The device to supply the blast with powder must be certain to feed 

 continuously and adjustable to api)ly as much or little as may be 

 desired, yet not capable of clogging. To produce such an effectual 

 arrangement for feeding minimum quantities of poison mixed with 

 materials which pack and clog easily, like flour, for example, was diffi- 

 cult, and for a long time threatened to be an impossibility ; but the prin- 

 ciples already noticed above apply here, and their employment in these 

 devices is described below; but it must be remembered that the blast of 

 the rotary blower is large and weak, while that of the oscillating blower 

 is small and intense, so some adaptive modification is advisable. 



A blast with an independent passage for itself is made to feed itself 

 by the attrition of its lateral parts or by a side blast. Thus the blast 

 force is utilized to cut out and carry the powder from the mass where it is 

 exposed for an area extended by a slot or a group of openings through 

 the segmental or interrupted svall between the blast passage proper and 

 the reservoir which adjoins or surrounds it. Thus a reliable positive 

 feeding force is directed and controlled without depending solely on 

 gravitation or on ordinary mechanical feeding devices, which will not 

 feed regularly in minimum quantities. This kind of apparatus works 

 freely and the direct unimpeded blast throws the powder a good dis- 

 tance. The blast thus acts to open the narrow feeding entrances. At 

 the same time a passage to deliver a part of the blast or another blast 

 simultaneously above the poison to produce a pressure downward upon 

 it assists gravitation, but is not necessarily employed, for, especially 

 where the bulk of the poison is small, the air will alternately and in- 

 termittingly force up through the poison, opposing gravity, and then 

 react downw^ard, assisting it. For flour mixtures the feeding is done 

 pretty well by passing the blast tube through the base of the powder- 

 can, therein providing the tube with numerous holes having one-eighth 



