230 RAILWAY CONSTRUCTION. 



The amount of cant, or super-elevation, to be given to the 

 outer rail on curves must be regulated by the speed of the train 

 and the gauge of the line. Many formulae have been compiled 

 to determine the necessary amount of super-elevation, but expe- 

 rience has shown that by some of them the calculated amounts 

 were excessive. Possibly during past years too much cant has 

 been given in many cases. The following simple formula 

 approaches very closely to practical experience 



(velocity in miles per hour) 2 x eauge in feet 



r . f T Q- = tion of outer rail 



radius in feet x l'2o . . . 



in inches. 



For high-speed trains uniformity of cant is of the utmost 

 importance, more so even than the exact amount. Any irregu- 

 larity in the super-elevation of the outer rail, sometimes high and 

 sometimes low, will produce a dangerous swaying movement in 

 the train, which, if not promptly checked, would lead to 

 derailment. 



More injury is done to curves by spreading, arising from 

 rigid wheel-bases of engines and tenders, than from any want of 

 counteraction to centrifugal force. 



When a long length of permanent way has been linked in, 

 rails spiked to gauge, and fish-plates bolted together, the plate- 

 layers can proceed to the final adjustment to line and level in 

 accordance with the stakes and pegs provided for their guidance. 

 The setting to exact line is effected by means of long pointed 

 round iron crowbars, which are struck forcibly into the ballast 

 alongside the rails, and serve as powerful hand-levers to pull or 

 push the rails to the right or left as directed by the foreman 

 standing some distance back at one of the line-stakes. The men 

 with the crowbars pass from rail-length to rail-length, until a 

 long stretch of road has been pulled into correct line. 



The adjustment to rail-level is done by first packing up the 

 sleepers to the correct height at the various level-pegs, and then 

 packing up the intermediate sleepers so that the surface of the 

 top of the rails forms one uniform even line from level-peg to 

 level-peg. On new lines it is usual to pack a little high in the 

 first instance to allow for the subsidence or compression which 

 invariably takes place on the passage of heavy trains over fresh 

 ballast. 



The form or contour line of the top ballast will vary 



