. en, to find the logarithms: As tangent 18° . . . 9-511776 Is to 620 6 2-792812 So is R 10-000000 To OB = 1910 feet . . 3-281036To find AD: As tangent 22° 9*606410 Is to 505-7 . . . 2-703895 So is R 10-000000 To AD = 1251-6 = 4^34t. . 3-097485 1910 (external secant 18° = -051462) = 1251*6 x (external secant 22° = -078535) = C E = 98*2 feet. PROPOSITION XYL Fig. 15. Let B he a point in a eiirve whose radius B F is piven^ and let D heanother fixed tangent point. It is required to find point of c. €., thecurve A B being produ
. en, to find the logarithms: As tangent 18° . . . 9-511776 Is to 620 6 2-792812 So is R 10-000000 To OB = 1910 feet . . 3-281036To find AD: As tangent 22° 9*606410 Is to 505-7 . . . 2-703895 So is R 10-000000 To AD = 1251-6 = 4^34t. . 3-097485 1910 (external secant 18° = -051462) = 1251*6 x (external secant 22° = -078535) = C E = 98*2 feet. PROPOSITION XYL Fig. 15. Let B he a point in a eiirve whose radius B F is piven^ and let D heanother fixed tangent point. It is required to find point of c. €., thecurve A B being produced, from which to start a curve to terminatein tangent at J)^ also the radius of last curve. Given the angles MDB, M B D, distance B D, and radius B the simple curve B C L to be run with a given radius B Ftill L N becomes parallel to D M. Now by the nature of a curve. I Locating Sidk Tracks, Exa 395 upon whatever point on the curve the transit be placed, the differ-ence between backsight on B and foresight on I, is alwa^s the. same, namely, -. Xovv^ at the true point of c. curvature 0, the difference between backsight on B and foresight on D is alsoB + D equal to - 2 -, therefore the transit reading the same on D as on L, OLD must be in the same straight line. Hence whenever the nature of the ground will admit of it, ececta flagstaff at D, curve round from B towards L until taking a back-sight the foresight necessary to fall upon L should strike the flagstaff,at D, The transit will then be at the point of c. curvature sought.! Then measure C D, and make this proportion; sine II C L*: ^ CD:: R?=rOD. Suppose H C L = 8°, and the distance C D = 600 feet. Then bysubstituting in the above proportion, we have by logarithms: As sine 8° = H C LIs to 4- C D = 300So is kToa-r= OD = 2855-0 9-143555 2-477121 10-000000 TS3356G * Because nCL -| COD. 396 FoRMULiB FOR RuNNING LiNES, When the ground will not admit of this method, ascertain bymeasurement or calculation the dist
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Keywords: ., bookcentury1800, bookdecade1850, booksubjectenginee, bookyear1856
