. 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 . indicates that the quantities between which it is placedare equal. The sign oo indicates that the difference of the two quantities be-tween which it is placed is to be taken The sign .•. stands for the word hence or therefore. The ratio of one quantity to another may be regarded as the quo-tient
. 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 . indicates that the quantities between which it is placedare equal. The sign oo indicates that the difference of the two quantities be-tween which it is placed is to be taken The sign .•. stands for the word hence or therefore. The ratio of one quantity to another may be regarded as the quo-tient of the first divided by the second. Hence, the ratio of a to 6 isexpressed by a : h, and the ratio of c to d by c : (/. A proportion expresses tlie equal it 1/ of two latios. Hence, . proportion is rcjiresentedby placing the sign — between two ratios ; as, a ■ b = c : d In the text and in the tables the foot has been taken as the unit gimeasure when no other unit is specified. FIELD-BOOK. CH/VPTER I. CIRCULAR CURVES. Article I. — Simple Cukaes 1. The railroad curves here considered are eitlier Circular or Paraholic. Circular curves are divided into Simple, Reversed, and Comj)Ound Curves. We begin with Simple Curves. 2. Let the arc ADEFB (fig. 1) represent a railroad ciuve, unit Fig. \.. 2 CIRCULAR CURVES. ing the straight lines GA and B FT. The lengtli of sudi a curve ismeasured by cliords, each 100 feet long.* Tlius, if the chords AD^DE, E F, and FB are each 100 feet in length, the whole curve issaid to be 400 feet long. The straight lines GA and BH are alwaystangent to the curve at its extremities, which are called tangent GA and BH are produced, until they meet in C, ^ C and B Care called the tangents of the curve. If ^ C is produced a little beyondCto /v, the angle KGB, formed by one tangent with the other pro-duced, is called the angle of intersection, and shows the change of direc-tion in passing from one tangent to the other. The following propositions
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Keywords: ., bookcentury1800, bookdecade1870, booksubjectrailroadengineering
