FUMIGATION OF CITRUS TREES. 21 



of the pole and at the same distance from the end as is the furrow 

 in a. A knot at the end of the rope prevents its removal from the 



hole. 



Most of the wear on the rope falls on the first 2 or 3 feet adjacent 

 to the pole, for this part is half-hitched each time over the tent. 

 ^See PI. Ill, fig. 1.) Some fumigators substitute a stout piece of 

 rawhide about 3 feet long to occupy this region between the end of 

 the rope and the pole. The rope should be |-inch or f-inch, and 

 about 3 feet longer than the pole. 



Derricks are necessary for very tall trees, which can not be covered 

 conveniently with poles. They consist of long poles having a frame- 

 work attached to the bottom by which to prevent slipping, as well 

 as to confine their movement to either of two directions while stand- 

 ing erect. There is a rope and pulley arrangement at the top for 

 raising the tent. The length of the uprights depends on the height 

 of the trees to be fumigated. They should be fully a foot higher than 

 the tallest trees. In California derricks average between 25 and 35 

 feet tall, having the top 2\ to 3J inches and the bottom 3J to 4^- 

 inches in diameter. Straight-grained Oregon pine is used. Their 

 construction is well shown in Plate III, figures 2 and 3. The frame- 

 work at the bottom (PI. Ill, fig. 3) is held together by bolts. The 

 tackle attached to the derrick in part consists of a pulley block fixed 

 to the top of the pole as shown in Plate III, figure 2. A ^-inch to 

 |-inch rope is attached to this pulley, passing through another pulley 

 block which is free, and thence back through the fixed one (see PL 

 VII). The rope used should be about three times the length of the 

 pole. When the derrick is to be moved from one tree to another the 

 free pulley should be hooked to a rope or ring on the standard, the 

 rope pulled taut, and the free end tied temporarily, as shown in 

 Plate III, figure 3. This will prevent the rope from becoming 

 twisted. The movable pulley should have a hook at the bottom 

 by which it can be attached to a ring on the tent. A guy rope several 

 feet longer than the derrick is fastened at the top of each upright 

 and is used in its manipulation. 



THE M ? FADDEN MACHINE. 



Mr. C. E. McFadden, of Fullerton, Cal., has devised an elaborate 

 and ingenious machine for placing tents on trees. A picture of this 

 machine is shown in Plate II, figure 2. In brief it consists of an iron 

 framework mounted on a pair of trucks. At the center of either end 

 of the framework is attached a long arm made of iron tubing. 

 These arms are comparable to a pair of long hoisting poles. Each of 

 these arms is raised or lowered by a system of steel cables passing 

 through pulleys attached to the arms and two high iron standards. 

 These cables are manipulated by a gasoline engine, which also oper- 

 ates another pair of cables used to raise or lower the tents to or from 



