96 BULLETIN 440, U. S. DEPARTMENT OE AGRICULTURE. 
permanent use. Of course, where rails are lifted and relaid often, 
there is a considerable current loss through breakage and kinking. 
Geared locomotives, with proper maintenance and repairs, are good 
for about 20 years service. During that period the boilers must be 
replaced once. A rod engine should, under similar circumstances, 
have a slightly longer life, say about 25 years. Cars, either skeleton 
or flat, have very little salvage value after being used five years. 
In operations of from 15 to 20 years in length it is generally necessary 
to figure that the log cars will be renewed at least once. 
The sale value of second-hand logging donkeys and similar equip- 
ment is very low. In first-class condition they will bring only about 
30 per cent of the original factory price, and after five or six years' 
use donkey engines can no longer be put in first-class condition. 
The wrecking value is even less. Logging donkeys are ordinarily 
good for about 9 or 10 years' service. In some instances they may 
be used as long as 12 years, but if not worn out in 10 years they are 
at least obsolete in type. 
The wrecking value of sawmills is likewise comparatively small. 
It is confined to the salvage value of the sawmill, planing mill, and 
dry kiln equipment. The lumber used in the buildings may have a 
small value in excess of the cost of removing it if the period of use is 
not too long. Depreciation commonly ranges from $1 to $1.50 per 
1,000 feet board measure, depending upon the amount of timber and 
the extent of the necessary construction. 
SUMMARY OF THE COSTS OF TYPICAL OPERATIONS. 
A more comprehensive idea of the cost of lumber production may be 
gained from cost summaries of typical operations of three kinds; 
namely, a small horse-logging operation, a medium sized circular 
mill operation, and a large band mill operation. The cost summaries 
given below are made on the basis of operations of average efficiency, 
in much the same manner as calculations of operating costs are pre- 
pared in appraisals of National Forest stumpage, and are checked 
by the actual costs of various going lumber companies. The costs 
of any particular operation may of course differ from these sum- 
maries. Costs are in each instance on the basis of lumber shipping 
tally. 
SMALL MILL SUPPLIED BY HORSE LOGGING. 
Operating costs: 
Logging— Per 1, 000 feet 
Felling, limbing and bucking $0. 75 
Horse skidding and swamping 1. 20 
Horse chute hauling 1. 40 
Chute construction 50 
