RAILWAY CONSTRUCTION. 235 



movements without curtailing the available standing-room for 

 vehicles on the lines and sidings. They are simple in con- 

 struction, do not require crossings, and in many cases save 

 a complete cross-over road. At the same time slip connections 

 can only be laid down where the angle of the intersecting lines 

 is sufficiently flat to admit of a connecting curve of workable 

 radius. 



Fig. 361 is an enlarged sketch of a set of ordinary 15-foot 

 switches or points. By placing them about the middle of the 

 stock rails the joints of the latter are kept well beyond the 

 sliding rails, and the road is held firmly together. It is neces- 

 sary to place the sleepers closer together at the switches to allow 

 for the reduction in section of the sliding rails, which results 

 from planing them down to the requisite shape. By substituting 

 two long timbers for the ordinary sleepers at the points of the 

 switch rails, as shown on the sketch, a more efficient support is 

 obtained for the switch-box or crank in the case of rod- worked 

 switches, and the working distance from the rails is accurately 

 maintained, irrespective of any packing or pulling of the road. 

 In the sketch a steel bull-head rail is shown on one side, and a 

 steel flange rail on the other, each bolted to an ordinary cast-iron 

 switch chair. Switch chairs are sometimes made of plates of 

 wrought-iron or steel, forged to the correct shape, and riveted 

 together. They are, however, much more costly than cast-iron 

 chairs, and deteriorate more quickly from corrosion. 



Fig. 362 is an enlarged sketch of an ordinary crossing similar 

 to the one indicated at C (Fig. 359), and composed of a cast- 

 steel reversible block. The ends and lugs, L, L, are formed to 

 suit the connecting rails and fish-plates, as shown in the cross- 

 sections. The casting is secured to the crossing timbers by bolts 

 passing through the side lugs, S, a cast-iron packing- washer, W, 

 being placed between the lug and the timber to ensure a solid 

 seat and avoid rocking. A very important point in the construc- 

 tion of these block crossings is to have the groove or flange-path 

 sufficiently deep to prevent the striking or touching of the flange 

 of a much-worn tyre. A well-made, carefully annealed steel- 

 block reversible crossing is very smooth in the road, and has a 

 long life. It is all in one solid piece ; there are no parts to work 

 loose or spread; the wear of the running surface is very uniform, 

 and when the one side is much worn down, there is the other 

 ready for service. The writer has had many of these steel-block 



