24 HYDROCYANIC-ACID GAS FUMIGATION IN CALIFORNIA. 



elaborately equipped of these recent innovations was devised by 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. Tins 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 (Ji) 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 (Ic) 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 H-gallon size is sometimes used for small trees 

 and a 3-gallon size for very large ones. A H-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, 



