228 RAILWAY CONSTRUCTION. 



chair road frequently have the spike-holes bored to template by 

 machinery, as indicated on Fig. 341. Steel or iron sleepers are 

 delivered with the recesses for rails, and holes for bolts or 

 fastenings formed complete by machinery. 



The distances apart of the sleepers will be regulated in a 

 great measure by the weight of the rails and the description of 

 the traffic. Where light rails are intended to carry heavy 

 engines the sleepers must be laid closer together than would be 

 necessary for heavy rails. The joint being the weakest part of 

 the rail, it is usual to put the sleepers closer together at that 

 place, with a view to gain additional support, to assist the fish- 

 plates in preserving as much as possible a firm unyielding surface 

 at the rail-joint. 



Fig. 343 shows an arrangement of sleepering largely adopted 

 for steel flange rails 26 feet long, and weighing 79 Ibs. per yard. 

 The length of a rail is more a question of convenience of hand- 

 ling, facility of transhipment, and general use, than of actual 

 manufacture. There is no difficulty in rolling rails up to 50 

 feet in length, or more ; but very long rails are extremely un- 

 gainly things to move about, and are more exposed to receive 

 permanent bends or kinks in unloading, besides requiring greater 

 spaces at the joints to allow for contraction and expansion. 



Fig. 344 is an example of sleepering for a chair railroad, for 

 steel bull-head rails 26 feet long, and weighing 85 pounds per yard. 



Line stakes and level pegs must be put in at suitable 

 distances to guide the platelayers in laying the rails to the 

 correct line and level, and on the curves the proper amount 

 must be marked off for the super-elevation of the outer rail. 



When the second layer of ballast has been spread for its full 

 width and depth the sleepers can be distributed, and the rails 

 or chairs spiked down to the correct gauge. Before putting on 

 the fish-plates spaces must be left at the ends of the rails to 

 allow for contraction and expansion, the amount depending upon 

 the temperature at the time of laying down the rails. As the 

 rails will expand, or increase in length, with the heat, it is 

 necessary to allow more space for expansion for rails laid down 

 in the cold, or winter months. On our home railways rails are 

 very rarely laid down when the temperature is lower than 

 25 F., or higher than 125 F., and this range of 100 may be 

 considered as covering all the variations likely to occur in 

 ordinary practice. The greater portion of the permanent-way 



