\fdO'^ - Old Forge Coal Mines

292 RAILROAD CONSTRUCTION.
(879)
(880)
See Art. 1508.
See Art. 1511.
(881 ) See Art. 1511 and Figs. 435, 430. 445, and 440.
(882)
See Art. 1513.
(883) See Art. 1514.
(884)
See Art. 1517.
(885) If the elevation of the grade of the station is
103 ft. and the height of the tunnel section is 24 ft., the
elevation of the tunnel roof at that station is 162 -f 24 =
180 ft. The height of instrument is 179.3 ft., and when the
roof at the given station is at grade, the rod reading will be
186-179.3 = 0.7 ft. Ans.
(886)
See Art. 1515.
(887) See Art. 1 51 7 and Fig. 448.
(888) See Art. 1520 and Fig. 452.
(889) See Art. 1523.
(890) See Art. 1525.
(891)
See Art. 1526.
(892) The area of an 18-inch air pipe is 1.5' X .7854 =
1.77 sq. ft. At a velocity of 13 ft. per second, the amount
of foul air removed from the heading per second is 1.77 X
13 = 23.01 cu. ft. And as each cubic foot of foul air removed
is replaced by one of pure air, in 1 minute the
amount of pure air furnished is 23.01 x 60 = 1,380.6 cu. ft.
As each man requires 100 cu. ft. of pure air per minute,
there will be a supply for as many laborers as 100 is contained
times in 1,380.6, which is 13.8, say 14. Ans.
(893)
See Art. 1528.
(894) See Art. 1533 and Fig. 455.
(895) See Art. 1535 and Fig. 457.