292 REPORT 4, UNITED STATES ENTOMOLOGICAL COMMISSION. 
coupling, and are entirely stiff throughout. The braucb, h t 1 may also 
be stiff, but in. case the arms are rigid it will generally be preferable 
that this main be flexible throughout, or at least in one of its junct- 
ures, h. Any or all of the three tubes forming the fork may be made en- 
tirely elastic by using hose-tubing with coiled or straight springs on 
the outside or the inside of the same. A straight piece of spring metal 
is generally preferable from being simpler and cheaper. In case any 
peculiar curve or position is to be given to the hose : tubes it may simi- 
larly be done by a rod having elastic or inelastic properties. To pre- 
vent such a rod from sliding out of its proper position in the tube it 
should be secured in at least one point. In Plate XLIX Fig. 5 is a 
sectional view of a fork showing how the rod may be inserted and fast- 
ened ; t is the insertion of the main, and j represents the arms or their 
coupliug-pieces, while y is the angle coupling, The rods to extend into 
the branches are indicated by s c. In this case they are shown with 
the one end s free while the two cross in the angle, and each has its 
other end riveted or soldered at c, in a hole drilled through the walls 
of the passage. Where the central piece is a casting this method is 
sometimes the best, but in Plate XXXIX, Fig. 4, a single rod, repre- 
sented by the broken lines s, extends around through both arms acting 
as a V-spring. Where the middle coupling is made by joining pieces of 
pipe [lb.. Fig. 5.], a rod of such shape is easily inserted before the parts are 
united. Other variations in the construction of these same devices can 
be thought out by any practical mechanic, and hence such need not be 
described here. When long sections of hose are used, where they tend 
to sag, bend, or kink as along the more or less horizontal supporting 
bar or frame, or in the nozzle-bearing arms, inside rods should be in- 
serted as supports. They are also of value to hold hose sections at 
any particular curve desired. The flexible sections or joint sheaths, 
e e, are easily made by any planter and require no special mechanical 
skill. The hose segment should fit tight upon the metal one and be held 
firmer by a single band or wire wrap, o, twisted or clinched tight around 
it. The flexibility of hose-coupled joints allows no breakage of the 
pipes, by permitting only tensile strain without lateral strain, rendering 
repair seldom necessary, whereas with stiff joints the segments are very 
liable to bend or break, especially at their ends, where weakened by tho 
thread cut for insertion in the screw-couplings. Stiff systems require 
the pipe to be several times heavier to prevent bending and breakage. 
Thus, aside from the economy in having much less weight, the lighter 
tubing costs less j and this reduction in weight and price allows the 
use of brass tubes, which are much preferable to heavy iron pipes that 
rust and are otherwise objectionable. Also, on this plan, even light zinc, 
iin, or other sheet-metal sections or angle-pieces which are not soldered 
Stiffly together, but arc easily separated or joined by any planter, can 
be employed. The lightest and cheapest apparatus can be made in 
tla se ways, and with the least amount of labor and skill in construct- 
