. Field-book for railroad engineers. Containing formulas for laying out curves, determining frog angles, levelling, calculating earth-work, etc., etc., together with tables of radii, ordinates deflections, long chords, magnetic variation, logarithms, logarithmic and natural sines, tangents, etc., etc . se formnltemay be safely used may be seen by the following table, which givesthe approximate values of Ffor several different values of n,n,D^and />, and also the error in each case. Compound Curves. Reversed Curves. n. D. 0 n. D. 0 V. Error. n. D. 0 «. 0 V. Error. 0 ; i\ 0 1 n 1 0 5 1 4 10 0
. Field-book for railroad engineers. Containing formulas for laying out curves, determining frog angles, levelling, calculating earth-work, etc., etc., together with tables of radii, ordinates deflections, long chords, magnetic variation, logarithms, logarithmic and natural sines, tangents, etc., etc . se formnltemay be safely used may be seen by the following table, which givesthe approximate values of Ffor several different values of n,n,D^and />, and also the error in each case. Compound Curves. Reversed Curves. n. D. 0 n. D. 0 V. Error. n. D. 0 «. 0 V. Error. 0 ; i\ 0 1 n 1 0 5 1 4 10 1 3 4 3 7 12 1 0 5 3 12 30 2 3 4 3 4 0 2 0 3 3 5 24 3 3 4 3 1 42f 3 0 3 3 4 30 3 h 0 3 3 45 1 1 5 3 13 20 2 I 1 4 0 40 2 1 29 1 3 1 20 2 1 4 9 4 0 2 3- 3 7 48 1 6 2 6 4 0 0 2 4 3 10 40 1 5 3 5 7 .U) 3 3 3 4 10 30 2 3 5 3 0 25f As the given quantities are here arranged, the approximate valuesof Fare all too great; but if the columns n and n and the columns Dand Dwere interchanged, and Fcalculated, the approximntc valuesof F would be just as much too small, the column of cnoi> rcniaiuingthe same. MISCELLANEOUS PROBLEMS. 63 83. Problem. To measure the distance across a river on a givenUraight line. D Fig. Solution. First Method. Let A B (fig. 33) be the required distanceMeasure a line A C along the bank, and take the angles B A C andACB. Then in the triangle ^1 C Cwe have one side and two angles to nnd A B. 1( A Cis of such a length that an angle A CB = ^D A C can helaid off to a point on the farther side, we have ABC=^DAC=^ACB. Therefore, without calculation, AB = AC.
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectrailroadengineering
