RAILWAY CONSTRUCTION. 



as the weight imposed on each rail by each driving- 

 Assuming this weight to be distributed over three 

 sleepers would give a dead weight of 3 tons per sleeper, or 

 134 Ibs. on every square inch of the 50 square inches of surface, 

 or rail-bearing area, on each sleeper, without taking into account 

 the effect of the blow or percussion from the rolling load. The 

 presence of a loose sleeper throws additional weight on the 

 adjoining sleepers, and increases the destructive influence on 

 the timber. The constant application of heavy rolling loads on 

 a small bearing area of timber crushes and wears away the 

 timber very rapidly. The small bearing surface of the flange 

 rail expedites the cutting down into the sleeper, and as the rail 

 beds itself further and further into the wood, the fastenings 

 must be driven or screwed down to follow the flange. Spikes 

 may be driven down, but the further they go they have a less 

 thickness of timber for a bed, and therefore a diminished hold. 

 Crab bolts are apt to become rusted or ironbound, so that they 

 cannot be screwed further, and must then be taken out and 

 replaced with new ones. The narrower the flange, the more 

 rapidly does the rail-seat cut down to a thickness inconsistent 

 with safety. The sharp edge of the flange-rail has a tendency 

 to cut a channel in the spike, and it is not at all an unusual 

 occurrence to find strong square shanked dog-spikes, which have 

 been thus cut into to the extent of a third or even half their 

 thickness. The comparative narrow flange places the spikes at 

 great disadvantage in point of leverage for holding down, and 

 this weakness is soon made manifest, particularly on curves, 

 where additional crab bolts or other devices are rendered neces- 

 sary to counteract the tendency of the rail to rock and tilt over 

 sideways. When the head of the rail cannot be kept in its 

 proper position, the gauge becomes widened, and an irregular 

 sinuous motion takes place in the running of the train. This 

 drawback has been found to be a serious matter where light 

 narrow flange rails have been adopted to carry comparatively 

 heavy, short wheel-base engines. In some cases wrought-iron 

 sole-plates, or even cast-iron bracket-chairs, have been introduced 

 to give more bearing surface on the sleeper and increased support 

 to the rail, but neither of the two methods give the same simple 

 complete hold to the rail that is obtained by the cast-iron chair 

 for the bull-head rail. 



On the other hand, the modern cast-iron chair for the bull- 



