24 HYDROCYANIC-ACID GAS FUMIGATION IX CALIFORNIA. 
elaborately equipped of these recent innovations was devised bv Mr. 
C. E. McFadden, of Fullerton, Cal., and is shown in Plate IV, figure 2. 
Some of its devices are very ingenious and well worthy of mention. 
The large box (a) in the middle of the wagon contains an acid carboy 
whose neck can be seen projecting above and into which is inserted 
a rubber hose (b) which leads backward and downward to the rear of 
the wagon. Pieces of lead pipe are attached to the ends of this hose, 
the free end of which (g) is equipped with a piece of rubber tubing 
and cut-off for regulating the flow of acid. The water is contained 
in the barrel (c) at the front of the wagon. A hose leads from the 
bottom of this back to the large vertical cylindrical object (d) to the 
left of the acid hose and adjacent to the wagon wheel. This cylinder 
is the graduate used for measuring water. The slender iron rod (e) 
seen projecting from the top of this cylinder is attached to a movable 
float. This rod is graduated so that each graduation is equivalent to 
3 ounces of water. The turning of a valve at the bottom of this 
cylinder allows the water to flow in, raising up the movable float. 
When the graduation on the iron rod shows that the cylinder contains 
the required amount this valve is closed and another opened which 
directs the water through a downward-projecting pipe into the gen- 
erator placed beneath. The cyanid is contained in the box (h) at the 
rear of the wagon. The wagon is also equipped with a thermometer 
and hydrometer. The upper and larger (/) of the two horizontal 
cylinders above the scales is a rotary device for reading the dosage 
schedule. The lower cylinder (Jc) contains a sheet of paper on which 
a record of the dosages used is kept. 
GENERATING VESSELS. 
In California earthenware vessels of the type shown in figure 12 
(p. 75) are made especially for, and are almost exclusively used in, gen- 
erating the gas. They are sold without a cover. The average capacity 
is 2 gallons, although a 1 ^-gallon size is sometimes used for small trees 
and a 3-gallon size for very large ones. A 1 -^-gallon generator will 
serve for a dosage of about 15 ounces of cyanid without boiling over, 
a 2-gallon generator for approximately 20 ounces, and a 3-gallon one 
for about 30 ounces, provided the cyanid is in average-sized lumps 
and not powdered. Where dosages larger than 30 ounces are required, 
use two generators, or three if necessary. 
GENERAL PROCEDURE. 
The process of fumigation consists of covering trees with cloth tents 
and generating beneath them a very poisonous gas called hydrocyanic- 
acid gas. As previously mentioned, sheet tents exclusively are used 
in California. After exposing a tree to the gas for a definite time, 
