250 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 



The blast-pipe and hollow piston-rod, s, bears the piston head, a, in the 

 cylinder, v. A handle, w, is formed on the pipe, and others, h, on the cylin- 

 der. The ends, h' h"^ of the cylinder should be convex or concave to give 

 stifiness to the sheet metal of which they in this instance are formed. 

 Also at the end, h'^ the piston-head, a, is prevented by the convexity 

 from approaching too close to the piston rod passage or its packing at 

 the neck of the cylinder, thus tending to keep the piston parallel with 

 the c^iinder or prev^eut its rocking in the same. The sides of the cyl- 

 inder are preferably double, in order that bruises of the outer wall 

 may not affect the smoothness of the inner wall, aud for other purposes. 

 The valves are of the kind described for my bellows heads above. 

 These incurrent valves are made near the ends of the cylinder, at oo^ 

 and they act in alternation. 



The piston head has flexible margins, which hug the cylinder loosel^^, 

 but more tightlj^ under the air i)ressure. To make these margins a belt 

 of flexible material, broader than the head, a, has its center shrunk by 

 a tight wire int^ a groove in the circumference of the head, or a pair 

 of flexible cups may be used joined base to base. The head is free to 

 slide on the piston-rod for a very short space between the two annular 

 flanges or bearings, which may be alternately applied to their iDackings 

 on the head. These packings could be free or attached to the flanges. 

 It may be observed that when the head is against the one flange there 

 is left open an entrance between the head and the other flange as an 

 inlet from one end of the cylinder into the piston-rod and blast pas- 

 sage 5 also that when the head is against the other flange said entrance 

 is shut off from that end of the cylinder, and there is uncovered another 

 opening at the opposite side of the head as an outlet from the other end 

 of the cylinder into the hollow piston and blast-pipe. When either the 

 cylinder or the piston rod is moved reciprocatingly with reference to 

 the other the pipe inlets are alternately opened and closed, the slip - 

 head of the piston acting as a valve in opposition to the end valves, so 

 that both strokes of the piston or cylinder discharge the blast, making 

 it constant. A piston-rod with a single inlet may be lised, so placed 

 that the slip causes it to appear firsL on one side of the head and then 

 on the other. The pump is calculated to be worked by the two hands, 

 one hand at tt, holding the piston or blast-pipe, while the other hand 

 at h moves the cylinder, v^ back and forth. Where this sort of pump 

 is combined in machines any method of giving reciprocating motion in 

 such machines will answer for operating it. 



In this connection it may be well to state that Mr. Henry Hunphre^ 

 ville, of xMountville, Pa., patented in 1880, 1881, and 1882, (So, 251886), 

 some air-pumps for spray-dampeners, the latter being very simple, but 

 not specially adapted for spraying upon plants, since only the old-fash- 

 ioned atomizing principle is used, and not in such shape as to discharge 

 upward. There are many air-pumps in the market, but such as are 

 specially needed for field use have not yet appeared in the trade. That 



