LOGGING IN THE DOUGLAS TIE, EEGION. 123 



log travels suspended from a trolley is the characteristic feature. 

 This arrangement results in both advantages and limitations. The 

 advantages in the main are the reduction of friction and the fact 

 that with a structure that costs very little as compared with a rail- 

 road or pole road logs can be yarded for long distances at a uniform 

 speed. The limitations are fixed by the strength of the line as 

 related to its own weight, the tension that has to be applied, and the 

 service required of it. The load imposed by a turn of logs, great as 

 it may be at times, is a small part of the normal burden. The tension 

 necessary to keep it from sagging to the ground is greater on long 

 reaches. That, combined with the weight of the line, in time 

 exhausts its tensile powers. 



These considerations, well understood by makers of wire rope 

 and machinery, weighed heavily on the layout of the first attempt 

 with this system. A thousand feet was the longest reach attempted. 

 Trial, however, chiefly inaugurated by loggers under the spur of 

 necessity, has demonstrated the practicability of longer reaches. 

 Difference in elevation of the two cable supports is the key to the 

 matter. This changes the forces on the line greatly, and as much 

 of the ground to be logged compels just this arrangement the method 

 has of late been successfully employed on two or three times the 

 distance originally proposed. Not always, of course, does topog- 

 raphy so lend itself. Intervening ridges may cut off the oppor- 

 tunity to stretch a cable for a long distance, or at least prevent the 

 line from taking the sag which safeguards it. 



Three methods which are used successfully are described. Two 

 of these require special engines, and the other gives the best results 

 when used in connection with a special engine. It should not be 

 understood, however, that they are the only methods that have been 

 used or that no other types of engines or line arrangements have 

 been thought of. These methods have been used the most, have 

 been given the most publicity, and probably represent the best 

 principles so far evolved. The use of overhead logging methods 

 for swinging or roading is dealt with under " Swinging." 



LIDGEBWOOD OVEEHEAD SYSTEM. 



The Lidgerwood overhead system consists of a standing wire 

 cable suspended either between two trees, known as the head spar 

 and the tail trees — ^the tree-rigged type (fig. 36) — or between a 

 portable steel head spar and a tail tree — ^the portable spar type. 

 In the tree-rigged type one end of the standing cable passes around 

 the tail tree, being held in place by spikes, or over a tree shoe (fig. 

 37) suspended on the tail tree, and then down to a stump, to which 

 it is made fast. The other end of this cable may be connected to 



