272 
LOGGING 
summer but if the grade is as low as 10 per cent they are used 
to best advantage during cold weather when they can be iced. 
During the warm season, horses often are used to drag logs 
in earth slides. Several logs are fastened together by grabs 
into a "turn" and a team is attached to the forward log. In cold 
weather animals can be wholly or partially dispensed with. 
Iced timber slides are most efficient and, therefore, may be 
used on the lowest grades; those lubricated with skid grease 
rank next; while dry timber slides are the least efficient. 
The following table of grades for running timber slides is from 
European practice:^ 
Material transported 
Per cent of grade 
Dry slide 
Ice slide 
Firewood 
20-35 
30 
15-20 
6-12 
3-6 
Crossties 
Logs 
Grades of 25 per cent are considered best for dry nmning 
timber slides in which large logs are to be handled, although 45 
per cent may be used on short stretches if the slide is buiJt strong 
and rigid. The minimum grade should not be less than 10 
per cent. 
Timber slides with maximum grades of 80 per cent and an 
average grade of 60 per cent have been operated, but are not 
desirable because of the heavy loss through breakage. 
CURVES 
Curves on slides must be laid out with reference to the length 
of material to be handled and the size of the chute. Sharp 
curves are always undesirable and especially so on steep pitches 
because the wear is excessive and logs are liable to jump out of 
the slide. 
It is necessary on 2- and 3-pole slides to elevate the outer 
timber, the amount of elevation depending on the degree of 
curvature, the grade and the character of material that is being 
1 From Forest Utilization, by Karl Gayer. (Vol. V, "Schlich's Manual of 
Forestry," p. 325.) ' 
