RAILWAY CONSTRUCTION. 45 



From the above memoranda it will be seen how greatly the 

 gradients affect the loads. For an important main trunk line, 

 with a heavy and frequent train-service of passengers and goods, 

 the introduction of steep gradients would not only reduce the 

 speed of the train-working, but would probably involve the 

 necessity of assistant engines over those parts of the line ; and it 

 may be prudent, where possible, to incur heavier earthworks, or 

 considerable detours, or tunnels, to obtain more favourable 

 gradients. For such a line the additional cost, and the extra 

 distance caused by a detour of a mile or more, will be of far less 

 importance than the interruption in the train service arising 

 from a serious reduction in speed or taking on assistant engines. 

 On many railways abroad there are very interesting examples of 

 long detours of several miles, carefully studied out to obtain 

 greater length and easier gradients, resulting in the construction 

 of lines over which the traffic can be worked without neces- 

 sitating auxiliary engine-power. On the other hand, there are 

 situations where steep gradients cannot be avoided, where 

 certain altitudes must be reached, and where there is no alter- 

 native but to face the inevitable. 



On secondary lines, and short branch lines, where the traffic 

 is not expected to be heavy, and where speed is not so im- 

 portant, it may be policy to economize outlay and introduce 

 steepier gradients than on the main line. 



Half a mile of a rather steep gradient is not felt so much 

 when it is situate midway between two stations, because the 

 attained speed of the train assists the engine over the short 

 distance to the summit ; but when it occurs as a rising gradient 

 out of a station, it forms a great check to the working, particu- 

 larly in bad or wet weather, when there is the risk of the engine 

 slipping, and the entire train sliding back into the station. 



Long steep gradients not only necessitate increased motive- 

 power for the ascending trains, but also require increased brake- 

 power, and precautionary measures for the descending trains. 

 Where passenger trains are fitted with continuous brakes, the 

 risk of losing control is minimized ; but with goods trains com- 

 posed of waggons, having only the ordinary independent side- 

 lever brake, it will be found absolutely necessary in many cases 

 to have additional heavy brake-vans for descending the inclines, 

 and these special vans, unfortunately, will form so much extra 

 non-paying weight to be hauled up on the ascending trains. Of 



