124 
BULLETIN 711, U. S. DEPARTMENT OF AGRICULTURE. 
a main cable extension (fig. 38) between the spar trees near the head 
spar by means of a block and fall tackle, the main cable being tight- 
ened with the aid of the engine ; or the main cable may lead through 
Fig. 36. — Location of equipment and improvements, Lidgerwood overhead system. 
a jack on the head spar (fig. 39) and then down to a stump, where 
it is connected. The latter is generally used in this region. The 
method of tightening is the same in both cases. The steel-spar type 
is provided with a steel head spar built upon the skidding car and 
carried with it. This steel spar car- 
ries all the head blocks and rigging, 
with all the lines reeyed and in place. 
A slack-pulling skidding or yard- 
ing carriage travels on the cable 
(fig. 40). being moved toward the 
head spar by the skidding or haul- 
ing line and toward the tail tree by 
the return or trip line. This car- 
riage also carries the slack-pulling 
line, which enables the engine to 
giye out the length of skidding line 
necessary to reach the logs lying to 
one side or the other of the overhead 
cable. Lines other than the main 
standing cable lead from their re- 
spectiye drums on the skidding en- 
gine through blocks on the head 
spar, or both the head spar and tail 
tree, and thence through the skid- 
ding carriage to their respective 
positions. In operation the over- 
head cable is stationary. An auxiliary engine is used to load the logs. 
This system of yarding is a product of the East, haying been used 
for a comparatively long time in the forests of the South ancl 
Fig. 37. 
-Tail tree, Lidgerwood over- 
head system. 
