240 REPORT 4, UNITKD STATES ENTOMOLOGICAL COMMISSION. 
a small bellows, v, with handles, h h, one of these serving as a discharge- 
spout, communicating, through the powder receptacle, p, to its deliv- 
ery at s. The bellows is made mechauically tight without nails, glue, 
or other soluble adhesives, and is very strong. After binding the 
leather into the peripheral groove of the heads by a stout wrap of wire, 
a marginal, flange-like projection of the metallic heads, t, and the border 
leather above the wire are clinched down over the wire. Thus the head 
and leather are mechanically bound together in the firmest, strongest, 
tightest, and most durable manner. Also, as hydraulic bellows these 
cannot be surpassed, and where used for spraying liquids, as in devices 
to be noticed below, or where employed in wet fields or driving rains, 
this independence of harm from moisture is an excellent characteristic. 
The suction- valve is a soft plate of leather caged, with little play, upon 
the inlqfc hole which is punched through the thin metal head. This 
hole is covered outwardly witli fine brass gauze, z, to prevent coarse 
bodies from sucking into the valve or parts beyond, and to prevent the 
outward air-pressure from forcing the leather plate to wrinkle or bulge 
out too much at the inlet. Instead of the many-punctured outer cover 
one or more slots will give similar advantages in the construction of the 
inlet. Also, the valve plate is inwardly caged by gauze or bars, prefer- 
ably by the former. This prevents the valve-plate from moving for off 
from the inlet, so that it. will close quick and never fail to overlap the 
margins on all sides, and it also preserves the flatness of the flexible 
valve-plate while allowing the outward pressure to strike its outward 
surface in a direct manner. Thus the valve is made very simple, light, 
and effective. The discharge may be taken from either end of the hol- 
low cleat or handle, h, but the arrangement shown will generally be 
preferred, in which the blast is discharged through the left hand, be- 
tween the powder-can, p, and the bellows, v. Thus the weight of the 
bellows tends to balance that of the powder-can and extension-pipe, 
rendering the tool more easily wielded than if the weight was more 
distant from the hand. The powder receptacle may have any suit- 
able form, but the bicoirc shape here shown is efficient, and seems the 
simplest to make. One end is truncate, opening by the large screw-cap 
or plug, y. The blast passage inside extends radially from the periphery 
to the apex, with an extension- pipe, i, beyond, terminating in the crook 
discharging at s. The extension piece is separable at r. The internal 
relations of the blast to the powder will be better explained by observ- 
ing Fig. 2, which is a sectional view taken longitudinally through the 
parts. The tube, e r, inside the can, has a slot in its side, and about 
midway in its passage is a shut-off device,,;. When this is set, partially 
closing the tubular passage, only a part of the blast goes through direct, 
and the rest is crowded out to grind away the powder exposed by the 
slot passages. The more of the blast thus crowded out, the more of the 
powder will be fed to and carried away by the blast. To allow this 
feeding by erosion, one, two, or more slots or rows of holes of size and 
