222 
LOGGING 
the skidding lines were then run from the skidder to the tail 
tree, the former being supported on the intermediate spar tree. 
The carriage was placed on the main cable between the tail tree 
and the intermediate spar and the logs were then skidded to the 
latter. When the area between these two supports had been 
logged, the trolley was shifted to the skidder side of the inter- 
mediate spar and the logs then brought to the railroad. Timber 
beyond the reach of the tail tree sometimes was skidded to it 
Fig. 68. — A Logging Chance showing the Use of an Overhead Cablewaj' 
System in bringing Timber over a Ridge by relaj'ing 
by animals and the range of the machine thus greatly increased. 
A special type of trolley which can automatically pass the sup- 
port on the intermediate spar has been put on the market and 
does away with the necessity of relaying the logs. The trolley 
has two track sheaves which ride on the main cable. Under 
each main sheave below the cable there is a smaller and wider 
sheave which is mounted on a pivoted arm which, by tension, 
holds the lower sheaves directly under the carrying sheaves. 
This prevents the trolley from leaving the cable. The support 
at the intermediate spar is triangular in shape, the base of the 
