TIMBEK GROWING AND LOGGING PRACTICE IN CALIFORNIA 29 
So far as the data presented go, and examination of many cutting 
areas both national forest and private confirms this view, low-speed, 
ground-lead yarding is a satisfactory method, although distinctly 
more damaging than animal yarding. The wheels average 71.5 per 
cent survival, the donl^ey engine 55.5 per cent. For that reason, if 
for no other, and despite the good points of donl^ey yarding, animal 
(wheel) logging on ground to which it is adapted should be encour- 
aged by all possible means. 
Fig. 9. — GROUND-LEAD YARDING VIEWED BY AIRPLANE 
Radiating skid trails destroy a considerable part of the young growth, but in 
the intervening sectors no material damage is caused, and the net result is reason- 
iably productive land, if fire is kept out. 
HIGH-LEAD YARDING 
Imported from the fir forests of the Pacific Northwest about 1917, 
the high-lead system of yarding spread rapidly in the California 
pine region, and in 1921, out of 25 important operations, 19 were 
using the high lead either wholly or in part. 
The equipment used is essentially the same as for ground-lead 
yarding, except that the main lead block is placed on a spar tree 
