ON AMERICAN PERMANENT WAY. 



597 



are intended to be run. If one vides at a rapid rate over a road adapted 

 in this respect for slow speed, he will soon discover the want of elevation 

 to the curves. John B. Henck, an American civil engineer of great 

 reputation for his ' Field-book for Railroad Engineers,' published many 

 years a^o, gives the following table for elevation of the outer rail on 

 curves, based on the question of centrifugal force tending to throw the 

 ear against the outer rail, and the elevation of the same above the inner 

 one to counteract it. Practical use of this table has demonstrated its 

 correctness. M in the table represents the speed of train in miles per 

 hour, and the elevation is given in decimals of a foot for the degree of 

 curvature and the speed of train M. 



ELEVATION OF OUTER RAIL ON CURVES. 

 John 15. Henck, A.M., C.E. 



Of course some of these figures are merely theoretical, and out of the 

 question practically. No one would expect to go around a ten-degree 

 curve at 50 miles per hour, but would reduce speed. 



The Atlantic and Pacific Railroad Company elevate the curve ODe 

 half-inch per degree up to a ten-degree curve which has an elevation of 

 5 inches, and all sharper curves are kept at this same elevation. This 

 corresponds very nearly with Henck's table for thirty miles per hour. 

 The elevation of outer raii is run off, on to straight track, a distance of 

 10 feet per degree of curvature. Thus for a two-degree curve the 

 distance on the tangent is 20 feet, and for a ten-degree curve it is 100 

 feet. There may be cases where reverse curves come close together, and 

 this rule cannot be strictly carried out ; but an endeavour is always made 

 in such cases, if possible, to secure at least 50 feet of level track on a 

 tangent. Where two curves in the same direction are connected by a 

 tangent less than 100 feet long, the elevation is carried through from 

 curve to curve without reduction ; and if the tangent exceeds 100 feet the 

 regular inclinations are made from each curve until they meet, or until 

 level track is reached. These illustrations will serve to show the varia- 

 tions in practice with different roads. The rules for elevation of course do 

 not apply in yard ti'acks. All rails for curves should be bent to the 

 proper curvature before being laid on the ties. 



Several different standards of gauge of track have been used on 

 American roads : 6 feet, 5 feet, 4 feet 8§- inches or 4 feet 9 inches (a 

 modification adopted for compromise cars), also the various narrow gauges, 

 from 2 feet 6 inches to '?> feet 6 inches. There is a considerable tendency 



