118 
BULLETIN 711, U. S. DEPARTMENT OE AGRICULTURE. 
One company has found that the base of the spar tree should be 
from 11 to 20 feet from the center of the track. To insure the work- 
men against injury certain precautions are taken. The main-line 
lead block is hung in a 2-inch strap, the pins and shackles of these 
blocks being extra large, A ;; safety " guy is rigged under the bight 
of the main line in such a way that the main line will be deflected 
in case any of the rigging breaks. The bark on the spar tree is 
removed for several feet at the point where the lead block strap is 
attached, thus preventing it from being dislodged when yarding 
is in progress. 
The general method of using a saw or ax to cut off the tops of 
trees selected for spars is both tedious and dangerous work. One 
company is using dynamite instead. The head rigger puts on a pair 
of long-spurred climbing irons and ascends the tree -to the desired 
height, taking several sticks of dynamite 
with him. The dynamite, which is tied to- 
gether end to end. like a string of sausages. 
is fastened securely around the tree at the 
point where he desires to remove the top. 
A detonating cap. to which a long piece 
of fuse is attached, is inserted in one of 
the sticks of dynamite. The rigger de- 
scends 20 feet or so. lights the fuse, and 
makes his way to a safe place on the 
ground some distance from the tree. After 
a few minutes the dynamite explodes, the 
tree top leaps into the air and comes 
crashing down. This way of removing the 
tops is only in the experimental stage at 
present. 
EQUTPilEXT. 
The equipment used in high-lead yard- 
ing differs little from that used in ground 
yarding. 
Yarding engines. — Any kind of two- 
drum yarding engines may be used. To take full advantage of 
the system, however, an engine with higher drum speeds than that 
of standard yarding engines should be used. One company, work- 
ing on good ground and in second-growth timber where the logs 
average about 600 feet in volume, has purchased yarding engines 
designed especially for this system. These machines are simple 
geared, with 11 by 17 inch cylinders. Both main and trip drums 
are driven directly from pinions on the crank shaft without the 
interposition of counter shafts or idlers. The drums are narrow 
and of large capacity. The increased length of stroke compensates 
Fig. 35. — Auto-lubricatin| 
high-lead block. 
