124 LOGGING 
(3) The distance. Animal draft is used both for short and 
for long distances. The efficiency of this form of draft decreases 
rapidly with the distance hauled on level ground and on large 
operations it is seldom profitable to skid or yard logs for distances 
greater than from 600 to 800 feet. However, logs from scattered 
bodies of timber or light stands may be hauled for much greater 
distances on some form of wheeled vehicle when the volume of tim- 
ber is so small that it is not profitable to bring the main transpor- 
tation within a few hundred feet of it. In a rolling region, the 
profitable skidding or hauling distance for animals may be much 
increased because of the greater volume of timber which can be 
moved down grade at one time. In such cases logs may be 
dragged for distances of 3/4 or 1 mile. 
Ground power skidding methods are rarely adapted to distances 
greater than from 600 to 1000 feet, and overhead systems from 
800 to 1500 feet. However, in very rough regions the latter 
type of equipment has been used for distances as great as from 
3500 to 4500 feet. The choice between the two methods is based 
largely on the volume of timber to be moved, the size of the units 
to be handled, the character of bottom over which the timber 
must be carried, and the form of primary transportation available 
both for moving logs and skidding equipment. 
(4) The form of primary transportation. Animal draft may 
be used with rail, motor truck or water transport but, in general, 
only two forms of power equipment have proved satisfactory when 
railroads are not available, namely, pullboat logging in cypress 
and tractor logging.^ Logs skidded by pullboats are floated to 
destination while those logged by tractor may be floated or else 
hauled on motor trucks. The latter practice is followed in tractor 
logging only on relatively small operations. 
(5) The annual or seasonal output. Some form of animal- 
draft is always used when the annual or seasonal output is small, 
because the investment in logging equipment is less and the ani- 
mals may be diverted to other work when logging is not in prog- 
ress. Power skidding machinery represents a large initial in- 
vestment and the capacity of such machines is too great for small 
operations. Few power skidding machines can be operated 
1 In some cases in the Pacific Northwest, power skidding is usejl without 
rail transportation, the logs being dragged to water transportation by road 
engines. 
