TIMBER USED IN CONTACT WITH SOIL. 49 



(better mild steel) plate, which is forced under pressure into the 

 form of a shallow trough of the same length and width as a half- 

 round -wooden sleeper. At the seat of each rail the metal is cut 

 obliquely away from the rail for a distance of a few inches, and 

 the cut ends are raised so as to form between them a chair between 

 ■which the foot of the rail fits. 



As far as present information goes, the following brief compar- 

 ison, point by point, between wooden sleepers and metal ones of 

 the trough pattern seems to be justified :■ — 



1. Appropriate form. — No practical difference. 



2. Resistance to fracture. — "Wood superior to metal. 



3. Resistance to lateral, longitudinal and vertical displacement. — 

 Trough sleepers superior, as they can be fixed deep in the ballast, 

 whereas to preserve wooden sleepers, these have to be kept ex- 

 posed to the air as much as possible. 



4. Durahility. — Life of trough sleeper estimated variously at 

 from 30 to 50 years. Steel rusts more rapidly than iron, which is 

 however liable to be forced out of shape. Sleepers of sound, well- 

 seasoned teak probably last for over 20 years. Merely adzed 

 sleepers cut from undersized logs, so that they contained the pith, 

 have been known to last 14 years, or about the same as the best sal. 

 Deodar requires renewing after about 7 years. Hardwickia hinata 

 will probably last as long as metal. Oreosoted fir and pine from 

 the Baltic rots in 2 or 3 years, sometimes even in the stacks be- 

 fore the sleepers can be placed in the line. Another source of loss 

 before use is due to the formation of large cracks in wood that was 

 previously quite sound. All wooden sleepers begin by being at- 

 tacked by dry rot on the lower concealed surface, and the progress 

 of the rot may be very advanced even when the visible surfaces 

 are quite sound. White ants sometimes attack wooden sleepers in 

 spite of the constant passing of trains. 



5. Cost of construction of permanent way. — Cheapness of the 

 one or the other kind of track depends on the local conditions and 

 the state of the iron market. 



6. Maintenance of gauge. — Metal superior. 



7. Cost of maintenance and renewal of sleepers. — The advocates 

 of the metal track contend that once it has set, it requires much 

 less labour to maintain than a track with wood ; and they also 

 adduce the fact, which is undeniable, that old discarded metal 

 sleepers fetch a much higher price than similar wooden sleepers. 

 But at the International Railway Congress held at Brussels in 

 September 1887, it was decided that sufficient data to come to any 

 conclusion do not yet exist with regard to lines with large and 



