224 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 



circumference on the ascending side. The objection to feeding at the 

 center is that, on account of gravitation, the spray is thrown more down- 

 ward than upward, whereas the ascending side entirely opposes gravita- 

 tion, and throws off the material before it is carried around to where 

 gravity can pull it off downward. 



If the brush be rotated in a cylindrical trough supplied with the 

 fluid, the latter is dipped out and thrown in too great volumes, unless 

 the quantity in the trough be kept at just such depth that too much 

 cannot be caught and lifted. To keep thus a constant shallow sup- 

 ply in the trough it may be fed by the automatic drip process, such as 

 is employed in automatic inkstands, &c. A tube from an air-tight 

 liquid reservoir descends into the trough near to its bottom. The 

 height of this drip orifice gauges the depth of the liquid; for when enough 

 flows to submerge this outlet air cannot enter it to press the liquid out, 

 and only after the brush has thrown out enough to lower it can more 

 air enter and the liquid again flow to the same level. 



This process is a little more difficult and complicated than the free 

 drip method, in which the trough may or may not be used. In the latter 

 method the amount thrown is gauged by the size of the smallest caliber 

 of the feed spout. 



Brushes may also be used as feeders or throwers of powder. They 

 may be used on sifters, to keep their small passages open and help rattle 

 the powder through them. Also a brush may be worked in a powder 

 reservoir or hopper to feed out the powder upon plants or into a blast 

 from a blower, to be swept thereby to the substances being injured by 

 insects. 



These brushes will throw powder to some distance and in an excel- 

 lently diffused cloud, but quite fine powder, like flour, &c., cannot be 

 thrown very far through the air, because the particles are so small as 

 to have little momentum, and soon become stopped by the resistance of 

 the atmosphere ; but coarser powders, like corn meal, sand, &c., are 

 thrown a much greater distance by the same force. Yet in either case 

 much more distance can be attained by encasing the rotary brush, or 

 reel, or wheel, in such a manner that it may ac^ as a blower, and throw 

 a blast of air along with the powder. The stronger the blast the farther 

 the powder will be thrown, and the coarser the powder the sooner will 

 it fall. In these respects it is seen that the thrower-discharge is the 

 opposite of the blower-discharge. 



Some machines involving the use of brushes need to be noticed here. 

 Plate XXVII, Fig. 1, represents in plan section a brush-machine of sim- 

 ple construction, and illustrates a method of encasing rotarybrushes to be 

 fed by powder or liquid, and in order to throw the same by the elasticity 

 of their bristles springing from beneath a surface against which they 

 are revolved. 



The cylindriform brush d, turns (in the direction indicated by the 

 arrow) in a trough open on the side, s, and bears the square powder-can, 



