On Railway Gradients. 115 



Atmospheric resistance, increasing with the square of the 

 the velocity of the moving body, assumes a power on a carriage 

 moving at a speed of one hundred miles per hour, equal to 

 that expended in overcoming the inertia of 180 tons on a level. 

 It is to be regretted, this subject has not received, at the hands 

 of engineers, that amount of consideration its importance 

 demands. 



Mr. H. Bessemer gives an account of a series of experiments 

 on the opposing power of the atmosphere. The conclusion he 

 arrived at was, that the resistance of the atmosphere equalled on the 

 leading carriage of a train, a power of 10 to 4, as contrasted 

 with the resistance offered individually by each trailing carriage. 

 Continuing these experiments he states — this latter force was 

 completely neutralised by filling in the spaces between the 

 ends of each carriage with hoods, making the train in appear- 

 ance one long carriage. 



This report is singularly at variance with the statements of 

 Mr. Wood, published by the British Association. There it is 

 stated, " the form of the front/' (i.e.) the leading carriage of a 

 train " has no observable effect, and that whether the engine 

 and tender be in front or two carriages of equal weight, the 

 resistance will be the same." 



It is further shown, that " converting the train into one un- 

 broken mass," by filling in the spaces between each carriage, as 

 adopted by Mr. Bessemer, was a " disadvantage" rather than 

 otherwise, and Mr. Wood concludes, "it is certain that no additional 

 resistance is occasioned by leaving open spaces between the 

 carriages." 



How such conflicting accounts can be reconciled, is a question 

 I will not discuss. Possibly Mr. Wood's experiments were 

 made on a comparatively calm day, with the motion of the air 

 uniformly with that of the train. 



I am inclined to think, that with a head wind, however slight, 

 the theory of Mr. Bessemer is the most accurate one, though, 

 doubtless, the results quoted are much exaggerated. 



According to the Chevalier de Pambour, the resistance of the 

 atmosphere to the passage of a train may be found thus : — 



V= Velocity of moving body, V 2 X • 002688= Atmospheric 

 resistance in lbs. avordupois per square foot. 



On a level well laid line of railway, Friction retards motion 

 to the extent of 61bs. per ton for carriages. This may be 

 assumed as a constant. 



The resistance due to Gravity, when the line of traction is parallel 

 to the incline, increases in uniformity with the grade, and equals, 



