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The main mast of tlie derrick is of spruce pine, about 35 feet high 

 for trees 30 feet in height, and stands between the rows to be treated. 

 To each side of it is attached a gaff 22 feet long, also of spruce pine. 

 The foot of the gaff clasps the mast with arms of oak, being raised 

 and lowered with double blocks and pulleys exactly after the manner 

 of a ship gaff. The top of the gaff is double blocked and pulleyed to 

 the top of the mast, so by means of its top and bottom attachments 

 the gaff can be raised to any height, its top many feet above the top 

 of the mast, if necessary, or it can be lowered to reach the ground. 

 Since it can take any angle of direction also it may be quickly 

 adjusted to trees of any height and at variable distances from the 

 mast. The top of the bell is attached by pulley near to the end of 

 the gaff. Three trail poles of hickory, each about 10 feet in length, are 

 fastened to one side of the lower border of the tent, their ends being 

 securely lashed to each other with rope, so that when they pull against 

 each other the rope and not the cloth will catch the strain. The cloth 

 is caught uj) and bagged slightly at these points of union of the trail 

 poles, as additional protection against tearing. The center of each of 

 these trail poles is connected with the top of the gaff by pulley, and 

 thus the border of the tent to which they are attached may be ele- 

 vated to any height, the opposite border swinging free within reach 

 near the ground. A trail rope is attached to each of the trail poles. All 

 pulley ropes belonging to the apparatus are secured to cleats on the 

 mast. 



In operation, when the mainmast, on rollers or wheels, has been 

 placed in position, the height of the tree to be fumigated and its dis- 

 tance from the mast are noted, and the foot of the gaff is raised or 

 lowered to the point of greatest advantage, as learned from experience. 

 If the trees of a grove are of nearly nniform height and at regular 

 distances apart one correct adjustment will serve for the whole grove. 

 A similar adjustment is made of the toj:) of the gaff, this operation by 

 necessity' being repeated with ever}' tree. The to^) of the tent is next 

 drawn fully up and then the three trail poles; the hanging free edge 

 near the ground and as much of the border as possible is now brought 

 into position and the top of the gaff lowered some if necessary. Slack 

 is now given to the trail poles, and a man at each trail rope so pulls 

 the pole to Avhich his line is attached that the whole tent drops into 

 position over the tree. The lower border of the tent must be extra 

 strong to avoid tearing. It is best bound with rope. To remove the 

 tent from the tree the i)rocedure is almost exactly reversed. With 

 men trained to work together the tent may be lowered over a tree in 

 seven or eight minutes and removed in about five. Since the opera- 

 tion of removing the tent from one tree raises it almost in position to 

 drop upon the next, the time required for changing will not be the 

 sum of eight and five minutes, but the last five minutes is divided 



