142 BULLETIN Til. U. S. DEPARTMENT OF AGRICULTURE. 
of its life when it was discarded and used for chokers. The wear 
on this line is much greater when yarding uphill or on level ground. 
Still, in no case is its life as short as the main yarding lines used 
for ground yarding. The haul-back lines in use range from nine- 
sixteenths to twelve-sixteenths inch in diameter. Straw lines are 
generally three-eighths inch in diameter. 
SWINGING. 
Among the loggers of the region it is generally considered good 
practice to build railroads within an economical yarding distance 
of the timber. It is not always possible, however, to do this. It- 
may be cheaper, because of the cost of railroad construction or the 
quantity of the timber, to use two or more logging engines, with or 
without improvements, to transport the logs from the stump to the 
landing. The practice of using two or more engines to transport 
timber over the ground — that is. without improvements — from the 
stump to the landing is known both as swinging and reading. In 
this publication the operation will be referred to as swinging, the 
distance from the yarding engine to the landing or pole road being 
considered as the swinging distance. The use of overhead logging 
engines for the same purpose will also be considered as swinging. 
The distance it pays to swing timber is governed largely by the 
topography and formation of the country and by the quantity of 
timber in the swinging unit that can not profitably be logged direct- 
to the landing. Under most conditions timber can be swung farther 
with overhead than ground logging engines. 
Swinging decreases the cost of railroad construction, but it in- 
creases the cost of transporting the logs from the stump to the land- 
ing. Theoretically speaking, it is the comparison of the cost of the 
two methods, taking into consideration the fact that the yarding and 
swinging at times delay each other, that indicates whether swinging 
should be resorted to in a given case. 
GEO VXD SWINGING. 
It has at times been found profitable to swing logs three or four 
thousand feet over the ground. At times it may prove cheaper to 
single-haul the timber 1,200 feet or more — if the drum capacity of 
the yarding engine will permit — than to double-haul it. At other 
times it is cheaper to double-haul a shorter distance than this. Xot 
infrequently two swing engines, in addition to the yarding engine, 
are used, and occasionally three swing engines are necessary. 
The distance between the swing engines depends to a great extent 
on the topography of the country, the aim being to place them in 
such a way that they will not hold up the yarding engine. Under 
