TRANSPORTATION 123 
West, namel}', logging engineering which calls into play a knowl- 
edge of the civil, mechanical and electrical phases of the profes- 
sion especially adapted to the loggers' needs. 
Transportation on a logging operation may be classified under 
two main heads, namely, secondary or short-distance, and pri- 
mary or long-distance. 
Secondary transportation. — This is used to bring the raw ma- 
terial from the stump to some central point or points from which 
it is taken by the primary transportation to the mill or market. 
It varies widely in character and the work may be done solely 
by manual labor, although animal draft or mechanical power 
is most frequently used. In general the choice of methods is 
based on some or all of the following factors: 
(1) The size of the timber, the stand per acre, and the length 
of logs desired. Very large timber such as redwood and Douglas 
fir can best be handled ])y some form of mechanical power, owing 
to the great weight which must be moved, hence power skidding 
or yarding machinery is used. 
Light stands of timber, unless the trees are of large size, can be 
logged cheaper by some form of animal draft than by mechanical 
power l^ecause the use of the latter usually necessitates the con- 
struction of an extensive mileage of logging railroad spurs, the 
unit cost of which is excessive when the stand per acre is low. 
Tractors have been introduced successfully on some operations 
in recent years as a substitute for animal draft in logging light 
stands. They have proved useful on long hauls and also on 
slopes, especially during the warm weather when steep ascending 
grades reduce the efficiency both of teamsters and animals. 
(2) The character of bottom and undergrowth and degree 
of slope. When the bottom is smooth and free from underbrush, 
animals can be successfully used for moving small- to medium-sized 
timber, but animals are not satisfactory when the bottom is 
swampy or there is a hea\y undergrowth present, because in 
the first case the animals mire badly, and in the second case 
an excessive amount of swamping is necessary in making trails 
and roads. Slopes in excess of 30 degrees are hard to log with 
animals because of the difficulty of controlling logs as they are 
yarded to the lower levels, and also due to the great exertion re- 
quired on the part of the animal when it ascends the slopes on the 
return journey. Power skidding is more satisfactory under such 
conditions. 
