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The main mast of the 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 up 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 
nearthe 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 uniform height and at regular 
distances apart one correct adjustment will serve for the whole grove. 
A similar adjustment is made of the top of the gaff, this operation by 
necessity being repeated with every tree. The top 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 which 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 procedure 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 
