Sleeper-blocks are generally cut from the upper part of the tree, and do not therefore consist of the best portion of the timber, yet sleepers made from the soft, coarse-grained Baltic wood, properly creosoted, will last from twelve to eighteen years in the line in this country, while uncreosoted they would perish from decay in six or seven. The benefit is great when, by adding from eightpence to a shilling for the cost of creosoting, the life of the sleeper may be doubled or trebled. Of course, there are countries, like the far west of America, where the lines pass through vast forests, and where sleepers may be had for the mere cost of cutting. Creosoting in those places would be out of the question, and would cost four or five times the value of the plain sleeper. It is found, also, that in tropical countries and in dry climates at high altitudes creosote loses its 214 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. [Illustration: Fig. 307, 308, 309, 310, 311, 312, 313]