192 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 
the hole to clog it. If a sharp center-punch be employed, the holes 
ought to be punched from the outer surface. In this manner, each hole, 
as approached upon the inner side, is upon an eminence where clogging 
materials find unstable equilibrium, and they cannot well lodge except 
between the holes. Though this may seem a small matter, very much 
trouble arises from its not being observed. 
The spray should generally be made to spread rather broadly, and 
can get its divergent or radiatiug form from the convexity of the face 
from which it is discharged ; but where the face is flat, as is sometimes 
advisable or necessary, especially where the face is made reversible, the 
divergence can be obtained by drilling a part or all of the holes in a 
somewhat radiating direction. Also, where the water is squirted with 
considerable force, a fine spray will be obtained, and with ample spread, 
by boring the holes straight through a concave face, or else in such a 
direction through any thick face that sets of two or more jets converge 
to a focus, and there collide to dissipate each other into a finely atom- 
ized condition. Using this principle, a well-dispersed spray of better 
volume and quality can be produced from a smaller number of holes of 
larger capacity, whereby they are less liable to choke. On this plan 
the best many-punctured force-pump nozzles of the future will probably 
be made. 
The rose sprinkler-heads of watering pots and nozzles are commonly 
provided with no openings except the narrow neck by which they join 
upon the spout, and this does not admit the removal of foreign matters 
which collect inside. The head should be made of easily separable 
parts, to allow the interior face of the perforated side to be cleaned, as 
will be seen in the patterns, some of which have the punctured face re- 
versible. Squirting through the perforations in an opposite direction 
cleans them without injury, while punching through them with any hard 
instrument is a slower process and sure to damage. 
It is advisable to strain the water before it is admitted to nozzles, of 
whatever kind, by some of the devices shown in combination with the 
various reservoirs for carrying it and pumps for forcing it, as described 
later in this report. There is always an advantage in strainers,, although 
they add to the machine an increased number of holes to be clogged, 
for, if fine enough, they soon clog ; yet it may be used for a longer time 
without stopping, and the damage to the fine perforations of the face 
by punching dirt out of them should be avoided. The strainer should 
be large, and does not have to be cleaned so often as would the nozzle 
proper; still, where the gauze surface is exceedingly fine, or where the 
fluid squirted is much laden with solid particles, the strainer may clog 
very quickly. 
Eddy-roses. — All the many-punctured heads may be improved upon 
by introducing the liquid in an eccentric manner, and parallel to a tan- 
gent to the circumference, to cause it to whirl inside, and thereby make 
less liability to clogging by keeping active any internal rubbish which 
