122 BULLETIN" *m, U. S. DEPARTMENT OF AGRICULTURE. 
tainty, and the results secured so far give distinct promise of further 
improvement. 
One operator has come to certain tentative conclusions with regard 
to the use and adaptability of overhead systems in coast timber, 
which may be summarized as follows : 
(a) That overhead systems have little advantage over ground 
yarding systems in level or slightly sloping country and that they 
are not so satisfactory as the high-lead system on short hauls. 
(b) That overhead logging can be successfully and economically 
employed on almost any kind of ground, provided the quantity of 
timber justifies the necessary expenditure for proper equipment. 
Some rough mountain sides have been logged from railroads at 
their base, and numerous other types of rough country have been 
logged at moderate expense that could not have been logged at all 
with other systems, practically considered. 
(c) That the length of overhead line which can be successfully 
employed depends on the support which can be given the line, the 
weight of the load to be carried, the size of the line, the grade of 
the line in operation, and the deflection of the line. T7ire rope is 
constructed to withstand certain pulls and stresses. The stress or 
tension on a cable suspended between two points is entirely different 
from that of any other type of rope application, and as a rule much 
greater than the stress expended by the suspended load. Too often 
conditions necessitate the use of an overhead cable with little sag 
or center deflection, and sag governs in a large measure the length 
of the cable. Putting it another way, the greater the deflection that 
can be secured the longer the cable that can be used. 
(d) That machinery designed and built for ground logging is 
not adapted for overhead logging. Ground logging machinery 
is built for power and to withstand strains. Furthermore, there is 
no elasticity in its make-up. Under certain stresses the engine or 
the line may break. Overhead logging engines, on the other hand, 
should have high-speed drums and be so constructed as to refuse 
to handle any load in excess of that allowed by the factor of safety 
in the overhead line. Under certain conditions excessive strains on 
the overhead cable can be prevented by the arrangement of the 
other lines. Engines adapted for both ground yarding and over- 
head or high-lead yarding can now be purchased. These have two 
speeds — one for ground yarding, the other for overhead or high-lead 
yarding. The slow-speed pinion can be shifted in one-half hour's 
time, the result being that a high-speed engine adapted for over- 
head logging is converted into a slow-speed engine for ground 
yarding. 
The bases of these conclusions are to be found in the peculiarities 
of the system. A wire hung between two supports along which the 
