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The fuel is necessarily consumed under great draught, so 

 that a very high temperature is produced, which rapidly 

 destroys the copper fire boxes and brass tubes of the 

 boiler. 



The driving wheels of the locomotive engine are subject 

 to great pressure, as well by the weight of the engine as by 

 the tractive power exerted through them, and at times to 

 considerable attrition on the rail. 



All these parts of the engine are very expensive, and 

 require frequent renewal. I believe the following are about 

 the times of the average duration of the various parts of an 

 engine doing average duty, but I hope to be corrected on the 

 point. The fire box lasts from 3 to 4 years, a set of tubes 

 from 9 to 1 2 months, the tire driving of the wheels about 6 

 months; the brasses require frequent renewal, and the fire 

 bars are sometimes destroyed in one trip. 



The weight of the engine and the rigidity of its springs not 

 only injures the engine itself, but more than any other cause 

 tends to displace and injure the rails ; in fact, in narrowly 

 watching a heavy locomotive passing at a high velocity, 

 the wheels may frequently be observed to jump upon the 

 rails. 



The locomotive is subject to the foregoing losses and 

 defects when travelling on railways of the best construction, 

 and on a level, or more favourable gradients ; but when a 

 severe gradient occurs, the wear and tear of the engine is 

 much increased, the weight of the engine itself absorbs the 

 more tractive power when such power is the most wanted, 

 and after a certain point of inclination, an ordinary loco- 

 motive is scarcely able to move itself. 



Such liability to slip depends much on the state of the rail, 

 which is most affected by a slight dew not amounting to rain, 

 or by a frost such as frequently occurs in the morning during 

 the spring and autumn. 



