\fdO'^ - Old Forge Coal Mines

RAILROAD CONSTRUCTION.
(QUESTIONS 878-946.)
(873)
(874)
(875)
See Art. 1503.
See Art. 1504.
See Art. 1504.
(876) See Art. 1505 and Figs.
426 and 428.
(877) As 60" F. is assumed as normal temperature, and
as the temperature at the time of measuring the line is 94°,
we must, in determining the length of the line, make an
allowance for expansion due to an increase of temperature
or 34°. The
equal to the difference between 60° and 94°,
allowance per foot per degree, as stated in Art. 1505, is
.0000066 ft., and for 34° the allowance per foot is. 0000066 X
34 = .0002244 ft. ; for 89.621 ft. the allowance is .0002244 X
89.621 = 0.020 ft. The normal length of the line will, there-
fore, be 89.621 + .020 = 89.641 ft. Ans.
(878) Let the line A B in Fig. 75 represent the slope
distance as measured, viz., 89.72 ft. This line will, together
with the difference of ^ c 88.986' A
'
elevation between the ^
extremities A and B,
viz. , 11. 44 ft. , and the
"
fig. n.
required horizontal distance A C, form a right-angled tri-
angle, right-angled at C. By rule 1, Art. 754, we have
sin A = ^^41 = .12751; whence, A = 7° 20'. Again, by
o9. 7/0
A C
rule 3, Art. 754, cos 7° 20' = g^nj^; whence, .99182 =
^^ and >4 C = 89. 72 X .
89.72'
99182 = 88. 986 ft. Ans.