136 BULLETIN 711, U. S. DEPAETMEXT OF AGBICULIUEE. 
Rigging. — The rigging consists of a main cable suspended between 
a head tree (fig. 43) and a tail tree (fig. 44). Upon this line the car- 
riage travels. Two lines only are required to operate the carriage; 
one to haul it in, the other to haul it back. The main cable, leading 
from a drum on the logging engine, passes through a block suspended 
near the top of the head tree, thence out to and over a tree shoe 
suspended en the tail tree, and then down to a stump, where it is 
made fast. The haul-in line, leading from a second drum on the en- 
gine, passes through a block on the head tree in the same way as the 
main cable, and thence to the front end of the carriage, where it is 
made fast. The haul-back or trip line, leading from a third drum 
on the engine, passes along one side of the run, then through a block 
on the tail tree, and thence to the back end of the carriage. 
The distance between the head and tail tree depends, of course, 
on the yarding distance, which in turn may be fixed by the practical 
range of the system. The system has been used successfully to yard 
logs a distance of 2,500 feet. The tail trees are from 150 to 300 feet 
apart, depending on conditions. 
Operation. — The haul-back line hauls the carriage out along the 
main line to the point where the log is to be hooked on. Then the 
main cable is slackened sufficiently to lower the carriage to the ground, 
the haul-back line being used to pull the carriage to the log when 
the log lies* to one side of the center of the run. When the choker or 
chokers have been attached to the carriage, the main cable is tightened 
until the front end of the load is raised far enough from the ground 
to clear obstructions. Powerful brakes on the main drum cable hold 
the main cable taut while the carriage with its load is pulled in. 
When the load is brought to the landing place, the main cable is 
lowered and then the load unhooked. The main cable is then tightened 
and the operation repeated. As logging on a run progresses, the cor- 
ner trip block has to be shifted. 
Logs can not be yarded from behind the tail tree, and it is difficult 
to yard logs on the outer edge of a wide strip near the tail tree. More 
power is required to raise the logs from the ground than with S} t s- 
teins having a taut overhead cable, since the engine has to raise the 
cable as well as the log. 
Changing lines. — One head tree is all that is required at each set- 
ting of the engine. The tail tree is changed each time a strip is 
logged, the new. tail tree being selected and guyed before the old cue 
is deserted. In changing lines, the lines are first drawn in to the 
head tree. The straw line, which is run before the change is started, 
is then used to run out the trip line. This operation takes from one 
to two hours. 
Equipment. — The equipment is much the same as that used with 
other systems of overhead logging. 
