LOCOMOTIVB ENGINE AN1> EAILWAT GBADIENTS. 161 



engines still further increased, that gradients of 1 in 30, or 

 probably 1 in 20, may be surmounted. 



The means necessary for the working of steep gradients, 

 appear to consist in the power of the engine and the 

 amount of the load which it has to overcome ; and, pro- 

 vided the latter is duly apportioned to that of the former 

 at a given velocity, there can be no doubt as to the work- 

 ing of steep gradients with considerable certainty and 

 effect. 



The power of the engine required in such cases will vary 

 according to the nature of the traffic ; but in every instance 

 where the distance is short and the transit is frequent, light 

 trains may be used and a less powerful engine employed. 

 At other times, where the traffic is less frequent and the 

 transit of heavy trains cannot be dispensed with, it then 

 becomes imperative to employ the most powerful engines, 

 so as to ensure certainty in surmounting the gradients, and 

 that, if possible, without the aid of an assistant engine. 

 Should the gradients, however, be long, and any of them 

 exceed 1 in 60, it may then be necessary under these 

 circumstances to employ an assistant engine as an auxi- 

 liary.* 



In every case of this kind, the generative power of the 

 engine at the minimum velocity, becomes a question of 

 considerable importance, as steep gradients cannot be effi- 

 ciently worked excepting under circumstances where a 

 plentiful supply of steam is at hand ; and hence arises the 

 necessity of employing engines of greater power, and boil- 

 ers of more than ordinary capacity, in the area of their 

 tubular surface, than those in general use, accompanied 



* Since the above was written, a gradient of nearly two miles in extent 

 has been opened on the East I^ncasbire Railway, between Accrington 

 and Hasliiigden, with a rise of 1 in 40. This gradient is worked with one 

 engine to the passenger trains at the rate of nearly 20 miles per hour, and 

 also with ordinary goods trains, excepting only in cases of wet weather and 

 heavy trains, when the pilot engine renders assistance. 



