New York Agricultural Experiment Station. 289 



]!reTent leakage of gas. The surface of the frame which rests 

 against the flange is also covered with the same material, fais- 

 tened on in the same manner, soi that when the movable side or 

 door is in place the two' surfaces of felt come together. Two flat 

 metal pieces projecting on each side of the base of the frame are 

 for the door to rest upon and prevent it from fitting into place 

 until it is forced tight against the top. Plate XLII, &. Thirteen 

 beveled buttons of oak force the door into place and press the 

 felts close together. The buttons are made of wood bolted on 

 and work on strips of tin to prevent tearing the canvas. The 

 buttons are forced into place by a wooden mallet, as shown at 

 Plate XLV. Metal binding handles such as used on cold-storage 

 doors answer the same purpose and are somewhat easier to oper- 

 ate, but cost more. 



COST OF CONSTRUCTION. 



The cost of a fumigator 10xGx6 feet should not exceed .|13, 

 if heavy 'sheeting is used to cover the frame. A good quality of 

 ware net, enough to line the upper half, will cost from |2.50 to 

 $4 additional. If eight-ounce duck is used the cost will reach 

 about 118. 



USE OF FUMiaATOR. 



OPERATING. 



A fumigator of this model, 10x6x6 feet, is easily carried and 

 operated by two men. A fumigator 12x8x8 feet, probably the 

 largest size of this style that would be practical, wonld require 

 three men. The removal of one side of the fumigator prevents 

 the necessity of lifting it up over the tree in order to put it in 

 place. It is placed over the tree in the manner shown at Plate 

 XLIII. At Plate XLIV the plan of setting off the charge is 

 shown. The bag of cyanide is placed over the dish of acid either 

 upon one of the cross braces or in the manner shown in the pic- 

 ture. A string tied to the bag extends through a small hole in 

 one o.f the upright strips of the frame. When all is ready the 

 string is gently pulled from the outside and the bag falls into the 

 acid. The hole is then closed with a tight-fitting wooden plug. 

 19 



