34 BULLETIN 1402, U. S. DEPARTMENT OF AGKICULTUEE 
HIGH-SPEED YAEDING 
As logging machinery has developed, the cry has been ever for 
greater and greater line speed and at present a rate of 1,000 feet 
per minute is claimed for some machines, compared with 250 to 
450 feet per minute for the older types. High-speed machinery 
may be used with the ground, low, or high-lead system, and is 
destructive with any one of them. Such yarding even without 
high lead may and often does approach in destructiveness the high- 
lead system. Incoming logs hit obstacles, such as clumps of re- 
production, with a smash that greatly increases the damage. The 
lighter and shorter logs especially do not liold the trail as they do 
with low-speed yarding, but whip around, tearing up reproduction 
on both sides of the trails and smashing into and breaking the 
larger trees. 
The Forest Service has tried this system experimentally on na- 
tional forest cuttings, and has been compelled to limit the speed of 
line to 500 feet per minute. Beyond this point destruction increases 
very rapidly, and a maximum of 600 feet per minute is all that is 
possible if lands are to remain in a productive condition. 
SKIDDER YARDING 
The steam skidders used in California pine are a specialized type, 
adapted to use only along railways. They are more readily moved 
than donlieys and in practice occupy a setting for a much shorter 
period than the latter. Skidders make a very characteristic pattern 
of straight, slightly radiating lines, a few from each setting (fig. 14), 
with no pronounced development of the inner zone of complete de- 
struction as in the case of much donkey logging. 
Most skidders operate with the lead block in an A-boom at an ele- 
vation similar to that under the modified lead, and when used with 
low-speed lines this is a satisfactory method. One large, two-line 
machine with high-speed line has proved very destructive, because 
of the characteristic whipping of the line and the smashing effect of 
incoming logs. Except for this the machine is acceptable, for its 
trails are clear-cut and narrow, cover only a small percentage of the 
ground, and leave the surviving reproduction well distributed. In 
practice, machines of this type have been used on level or gently 
sloping ground, where railway spurs can be built cheaply and close 
together. On such land, which is perfectly adapted to animal yard- 
ing, the use of any type of machinery is unfortunate, since damage 
is nearly always greater than if animals were used. 
A modification of skidder logging, as used in the Southwest, 
where logs are skidded into runways by teams and yarded in a 
straight line to the landing, seems to be the least destructive method 
of power logging. This system might be used in the California re- 
gion, unless size of logs proves to be too great. 
TRACTOR LOGGING 
Caterpillar tractor logging, though a recent innovation in Cali- 
fornia pine, already displays great possibilities and is likely to re- 
i:)lace in part big-wheel, donkey, and skidder yarding. The most 
effective layout seems to be 10-ton tractors of the tracklaying type, 
