\fdO'^ - Old Forge Coal Mines

SURVEYING. 247
this angle by 5, the degree of the curve, we obtain the
33 1
length B G D oi the curve in full stations. -^ = 0.62
o
stations = 662 ft. The length of the curve, 663 ft., added
to the station of the P. C, viz., 16 + 97.17, gives 23 + 59.17,
the station of the P. T. at D.
(672) The given tangent distance, viz., 291.16 ft., was
obtained by applying formula 91, T—R tan ^ / (see
Art. 1251), /=20° 10', and | /= 10° 05', tan 10° 05' =
. 17783. Substituting these values in the above formula, we
have 291.16 = /?
291 16
X .17783; whence, R = ^rp,= 1,637.29ft.
Ans.
The degree of curve corresponding to the radius 1,637.29
we determined by substituting the radius in formula 50
R = -.—p: (see Art. 1249), and we have
^ "
89,
sm D
1,637.29 = -^—n\ whence, sin D = ^-^^, = .03054.
'
1,637.29
sm D
The deflection angle corresponding to the sine .03054 is
1° 45', and is one-half the degree of the curve. The degree
of curve is, therefore, 1° 45' X 2 = 3° 30'. Ans.
(673) Formula 92, ^=^- (See
Fig. 283.)
Art. 1255 and
(674) The ratio is 2; i. e., the chord deflection is double
the tangent deflection. (See Art. 1254 and Fig. 283.)
(675) As the degree of the curve is 7°, the deflection
angle is 3° 30' = 210' for a chord of 100 ft., and for a chord
ot 1 ft. the
210'
deflection angle is ^^ = 2.1'; and for a chord of
48.2 ft. the deflection angle is 48.2x2.1' = 101.22'=l° 41.22'.
(676) The deflection angle for 100-ft. chord is ^-^ =
3° 07i' = 187.5', and the deflection angle for a 1-ft. chord is