ON RAILWAY CONSTANTS. 263 



five and a quarter seconds ; but, iu fact, these differences are quite insignifi- 

 cant, and equal ones would no doubt have been observed had the train been 

 allowed to descend twice over in the same condition. It is evident then that 

 no appreciable change in the resistance arises from closing up the intervals 

 between the carriages composing a train. 



The inevitable inferences to be drawn from the foregoing experiments are : 



1. That the resistance of a train is neither lessened nor augmented by- 

 changing the shape of its front or hind ends from flat to pointed surfaces, 

 with the view of rendering it thereby more capable of cutting through the 

 air. 



2. That whether an engine and tender, or two carriages of equal weight, 

 precede the train, the resistance is the same, and consequently the engine has 

 no effect upon the air, similar to that which the bow of a ship has upon the 

 water through which it is carried. 



3. That increase of frontage, independent of any increase of the general 

 magnitude of the train, does not increase resistance. This proposition, at 

 least, must be considered as true within the limits of the surfaces which were 

 actually submitted to experiment; the lesser surface being equal to the 

 transverse section of a train suitable for a railway of 4 ft. 8^ in. gauge ; the 

 greater surface equal to the transverse section of a train suitable for a seven- 

 feet gauge, such as the Great Western. 



4. That no additional resistance is occasioned by leaving open spaces be- 

 tween the carriages, confining the intervals to the dimensions allowed in prac- 

 tice, and that no advantage is gained by converting the train into one un- 

 broken column. 



Having proved that the excess of resistance, after deducting friction, re- 

 quired for its estimation something besides the elements of the dimensions 

 and form of frontage and of continuity of surface, it became an important 

 subject of inquiry, what was the element, as yet not taken into account, which 

 exerted the powerful influence observed. 



The reader will doubtless have perceived that the subjects of the experi- 

 ments hitherto desci'ibed were carriages all of equal magnitude and of almost 

 equal weight. When, however, the Committee first commenced their inquiry 

 they made an experiment on the Madeley Planes with a train of five waggons. 

 These waggons were loaded with iron chairs, so as to weigh precisely six 

 tons each. They were constructed with high sides and ends, capable of being 

 removed and laid flat upon the platforms of the waggons, so as to expose a 

 greater or less bulk of cari'iage alternately to the air. When the sides were 

 up, the whole frontage or transverse section, including the frames, wheels, 

 springs, and axle, amounted to 47*8 square feet. When the sides were re- 

 moved the transverse section was only 23*8 square feet, the surface being 

 diminished by the area of the front board, whose dimensions were eight feet 

 by three feet. The train, with its sides up, was placed at the 57th stake, at 

 the summit of the plane falling one in 177, and was allowed to descend by 

 gravity from a state of rest. It moved along the successive gradients, and 

 finally stopped 10,019 yards from the point of its departure. 



The sides were next removed and laid upon the platforms of the waggons, 

 and the experiment was repeated. The train came to rest at 14,058 yards 

 from the point of its departure. 



Minute details of these two experiments will be found in the Eighth Re- 

 port of the British Association for the year 1838. The value of the results 

 was only properly understood after the course of the previously mentioned 

 experiments had been completed, and the observations analysed. Frontage 

 alone was before considered to have produced the additional resistance cor- 



