RAILWAY CONSTRUCTION. 43 



gradients, may be expressed in various ways. A very general 

 method is to state the number of feet, metres, etc., which can be 

 measured along the gradient before an increased rise or fall of 

 one foot or metre, etc., is obtained. Thus a gradient of 1 in 200 

 signifies a rise or fall of 1 foot in 200 feet, or 1 metre in 200 

 metres. 



Sometimes the rate of inclination is expressed by stating the 

 number of feet of rise or falHn a mile. In this way a gradient 

 would be described as falling at the rate of 30 feet in a mile, 

 rising at the rate of 20 feet in a mile, etc. Twenty feet to a 

 mile is equal to 1 in 264. 



"Another method is to give the percentage of rise or fall. In 

 this way the inclination would be expressed as a 1 per cent, 

 gradient, 2 per cent, gradient, per cent, gradient, etc., which 

 for comparison would signify 1 in 100, 1 in 50, and 1 in 200 

 respectively. 



The gradients of a railway most materially influence its 

 facility and cost of working, and every effort should be used to 

 make them as easy as possible consistent with the prospect of 

 the line. 



Steep gradients signify heavy locomotives, increased cost of 

 motive-power, reduced speed, and light loads. 



The following tabulated memoranda show the approximate 

 loads, exclusive of engine and tender, which can be hauled on 

 the level and on certain inclines at various speeds by engines of 

 the quoted capacities and steam admissions. A medium-sized, 

 ordinary type of passenger and goods engine has been selected 

 for each of the examples. The working of the passenger engine 

 and train is assumed to be under favourable circumstances, with 

 fine weather, fairly straight line, first-class permanent way, 

 modern rolling-stock with oil axle-boxes and perfect lubrication, 

 and all the conditions most suitable to ensure the least resistance 

 to the moving load. For the goods engine and train a greater 

 resistance per ton of load is assumed, as the goods trucks are 

 never so perfect or easy in the running as the passenger 

 carriages. A certain amount of side wind is taken into con- 

 sideration, and also an allowance for moderately sharp curves, 

 the object being to indicate what may be looked upon as fair, 

 average, workable loads. 



The loads for engines of larger or smaller dimensions, or 

 higher or lower pressures, may be obtained by working out the 



