214 RAILWAY CONSTRUCTION. 



in dry climates at high altitudes creosote loses its efficiency, and 

 in those districts the best creosoted soft-wood sleeper perishes 

 from a species of dry rot in three or four years. Where wood 

 sleepers have to be used in tropical climates it is better to obtain 

 them from the timber of the district, although in many cases 

 suitable trees are difficult to procure and the cost of land 

 transport is very heavy. 



The soft cushion-like effect of a sound, properly packed 

 wooden sleeper contributes so largely to form an easy, smooth- 

 running road, that so long as they can be obtained at a moderate 

 cost, and are fairly durable, wooden sleepers will always be 

 preferred to those of any other material. The great question 

 will be the supply. Creosoting and other wood -preserving 

 processes have done much to prolong the life of sleepers, but the 

 rapidly increasing extent of mileage throughout the world, 

 together with the enormous number of sleepers required annually 

 for maintenance or renewals, must before very long severely tax 

 the powers of supply. 



In the great timber-producing territories the axe is often 

 heard, but the planter is rarely seen. Vast forests are cleared 

 away, and their sites transformed into busy towns or cultivated 

 lands ; and unless some great change takes place, and planting be 

 carried out on a large scale, some other material will have to be 

 adopted for this important item of our permanent way. 



Appearances would indicate that at no very distant date 

 iron or steel will take a conspicuous part in the formation of 

 future railway sleepers. 



More than thirty years ago several descriptions of cast-iron 

 sleepers were introduced into notice and tried on some of our 

 leading home railways. Cast-iron was at that time considered 

 more suitable for the purpose than wrought iron, as it was very 

 much less costly in price, and could be readily worked into any 

 desired form or size, with the advantage that the castings would 

 all be duplicates of one another. 



Figs. 307 to 313 show some of the types that were designed 

 and laid down in the road. In Fig. 307 the sleeper and chairs 

 were all cast together in one piece ; the rail was held in its place 

 by wooden keys, and the gauge of the line was maintained by 

 transverse wrought-iron tie-bars. The sketch represents one 

 of the sleepers used at the rail-joints, and has three chairs, the 

 larger one in the centre being for the support of the ends of 



