14 BULLETIN 77, U. S. DEPARTMENT OF AGRICULTURE. 



Table 7. — Amounts by species of round mine limbers produced in Colorado in 1911. 



Species. 



Lodgepole pine 



Engelmann spruce. . . 



Douglas fir 



Western yellow pine. 



Limber pine 



Bristle-cone pine 



Aspen 



Alpine fir 



Blue spruce 



White fir 



Oak 



Amount. 



Total 36, 274, 000 



Boardfeet. 



23,421,000 



8, 242, 000 



2,244,000 



1,354,000 



431,000 



183,000 



149,000 



109,000 



75,000 



65,000 



1.000 



Percent- 

 age of 

 total. 



100 



Table 8. — Unit costs for various diameters. 



Diame- 

 ter. 



Cost per piece 16 

 feet long. 



Cost per linear foot. 



Cost per inch of 

 diameter 16 feet 

 long. 



Inches. 

 3 

 4 

 6 

 8 

 10 

 12 

 14 

 16 



$0.35 



. 40 to $0. 50 

 . 45 to .65 

 .60 to 1.25 

 1.15 to 1.60 

 1.50 to 2.15 

 2. 00 to 2.25 

 2.50 



$0. 022 

 . 025 to $0. 031 

 .028 to .041 

 . 038 to . 078 

 . 072 to . 100 

 . 094 to . 135 

 .125 to .141 

 .156 



$0. 117 

 . 100 to $0. 125 

 .075 to .108 

 . 075 to . 156 

 .115 to .160 

 . 125 to . 180 

 .143 to .161 

 .156 



Table 7 shows that lodgepole pine is the main source of supply for 

 round mine timbers, and, together with Engelmann spruce, makes up 

 88 per cent of all the props cut. Douglas fir, although a very desir- 

 able wood, formed only 6 per cent of the total. 



COSTS FOR DIFFERENT SIZES. 



Table 8, giving costs for props of various diameters, was compiled 

 from such data submitted by the operators as were definite in regard 

 to the size of the material. Several methods of purchasing round 

 material were reported — cost per piece for a given length and diam- 

 eter, cost per linear foot for a given diameter, and cost per inch of 

 diameter at the small end for a given length. A large majority 

 reported the cost per linear foot. 



LIFE OF TIMBERS. 



There was a large variation in the reported life of timbers in the 

 different mines, especially in the metal mines. The timbers in the 

 coal mines had an average life of only about one-half that found in 

 the metal mines, but their size was also only about one-half as great. 

 Tables 9 and 10 give the average values obtained from statements of 

 the operators. 



