462 



REPORT — 1891. 



Table 2. 



3. Steep-grade Inclines on Mountain Bailivays. 



By Robert Wilson, F.E.S.E., M.Inst.C.E. 



The study of physical geography shows that, with few ex- 

 ceptions, plains or valleys, with a more or less varying rise 

 from the sea-coast, penetrate into the heart of the wildest hill- 

 country, the inclination of the ground becoming steeper as the 

 recesses of the range are penetrated. The rise of the ground 

 is most abrupt, often ending in precipitous faces of rock, or 

 steep bluffs of softer material, when nearing the saddles or 

 dividing-lines of the watershed at which these valleys cu.lmi- 

 nate. This almost universal feature is taken advantage of in 

 laying out roads and railways through a mountain country : 

 the solid, or sound ground, which is to be usually found on the 

 banks of the rivers traversing these valleys is naturally chosen 

 for the location of such works, and, in the instance of a road, 

 this permanent ground may be sometimes adhered to even to 

 crosshig the highest point on the saddles. 



But this is rarely possible in locating a railway-line, as the 

 satisfactory limit of grade is about 1 in 40 for any ordinary 

 locomotive engine depending for its haulage-power on the 

 adhesion between the driving-wheels and the rails. As the 

 declivity of the valley increases beyond this grade, which is 

 usually the case some miles from the dividing-ridge of the 

 watershed, the location of the railway must of necessity leave 

 the bottom of the valley and be taken on to the side of the 



