LUMBERING IN PINE EEGION OF CALIFORNIA. 33 
life under most conditions throughout the rest of the Sierras is one 
season for the main line and two seasons for the back line. Under 
favorable conditions in the central Sierras, where the soil is loose, 
the average life of the main line is eight months. On other opera- 
tions where large machines are used on rough chances the average 
life is from two-thirds to one season for the main line and two sea- 
sons for the back line, with considerable splicing. Usually it will 
not be far wrong to estimate an average life of one season for main 
lines and two seasons for back lines. Main lines on Dolbeers last 
only about two-thirds of a season and the same is true for very 
large yarders working under severe conditions. 
In addition to cables, supplies and repairs are included in mainte- 
nance. Supplies consist of oil, grease, tools, blocks, repair parts, etc. 
The amount required is of course larger for the larger machines. The 
cost per 1,000 is, however, much the same in different operations 
under similar logging conditions without much regard to the size of 
the operation. As a rule, it is from 6 to 9 cents per 1,000. The cost 
of repairs varies to some extent with the size of the operation. Large 
operations ordinarily have more efficient shops than smaller ones. 
The repair crew at the usual donkey camp of from three to five ma- 
chines is one donkey doctor, one blacksmith, and one blacksmith's 
helper. At some of the smaller camps the helper is eliminated. On 
other operations one donkey doctor may look after the machines in 
two camps. The board and wages of the repairmen amount to from 
8 to 10 cents per 1,000, of which it is judged about four-fifths is charge- 
able to yarding. In addition some of the heavier repair work is done 
at the mill shop. Also one or two machines are usually overhauled 
and repaired at the shop each year between logging seasons. Giving 
consideration to all these factors the information at hand indicates 
that the cost of maintenance in donkey yarding is normally from 18 
to 22 cents per 1,000. 
OVERHEAD YARDING. 
The use of this system has only just begun in the sugar and yellow 
pine region. Many operators are considering it as a means of re- 
ducing operating costs, but they do not feel that the machinery now 
on the market meets their requirements. A few loggers have been 
trying out systems of their own devising during the last two seasons, 
and one or two standard rigs have been employed. 
Two main systems are in use in the large timber of the Pacific 
Northwest. Both are alike in principle, having a main or standing 
one supported at either end, upon which a carriage is operated. In 
one system this main line is slacked off in order to allow the logs to 
be attached to the carriage; then the main line is tightened, which 
57172°— Bull. 440—17 3 
