1 52 MB. WILLIAM FAIEBAIEN ON THE 



with a large fire-box and increased powers of vaporiza- 

 tion. 



In the discussion of this subject, it may be necessary to 

 enquire into the laws which regulate the different elements 

 of resistance to which the locomotive engine is subjected ; 

 and, subsequently, to determine how and in what manner 

 those resistances are to be overcome. 



It is well known from practical experience, and also from 

 the experiments of Dr. Lardner, the Comte de Pambour, 

 and Mr. Woods, on Railway Constants, that the resistances 

 are — 



1st. The resistance due to friction in the working parts 

 of the engine, and the engine itself considered as a carriage. 



2d. The resistance of the carriages, waggons, &c., com- 

 posing a train. And, 



Lastly. The resistance of the air. 



In calculating the friction of a locomotive engine, two 

 considerations present themselves ; first, the friction of the 

 mechanical organs of the engine considered as a machine ; 

 and, secondly, the friction of the engine when considered 

 as a carriage. 



From a series of experiments by Pambour these elements 

 are separated ; but, taking the friction of the whole engine 

 at 104 lbs., and the average weight at 8 tons, we then have 

 on the datum of 6 lbs. per ton for carriages, a resistance of 

 56 lbs. for the mechanism of the machinery, and 48 lbs. 

 for the engine when considered as a carriage. Taking, 

 therefore, the united powers of resistance at 13 lbs. per ton 

 as a constant, we cannot be far wrong in estimating the 

 friction of the engine alone at 13 to 15 lbs. per ton, or 

 about two and a half times the friction of a railway waggon. 



From the above, it will be observed that the resistance 

 of the motive powers being given, we have next to consider 

 the resistance of a train of carriages and waggons. This 

 retarding force is variously stated by different authors; but 



