TRANSACTIONS OF THE SECTIONS. 191 



inclusive of brake-power, friction, and gravity, which latter force comes also into 

 operation either positively or negatively, according as the stop is effected on an 

 ascending or descending portion of the railway. 



The retarding force assumed as uniformly acting throughout the period of the 

 stop, such as friction, or brake-power, or gravity, or all combined, can therefore be 

 compared with and measured by the force of gravity acting on a gradient opposed 

 to the motion of the train. 



That force, as measured by the supposed gradient, admits of being expressed 

 in various ways, but preferably for our purpose (as we considered) by referring the 

 vertical height of the plane to its length as a percentage of the latter. 



The figure representing that percentage will of course also represent the effect 

 of gravity on that plane ; and is therefore the coefficient of the weight of the 

 train. . 



The course of our experiments, which extended over the period of a week, 

 comprised several series: one for ascertaining the friction of the carriages and 

 van*, apart from the application of any brake or other retarding power under the 

 control of the attendants; another for determining the frictional resistance of the 

 engines and tenders ; and lastly one for measuring the value of break application 

 under varied combinations. 



1. Fbiction of Carriages. 



Six trains of fifteen vehicles each, but detached from their respective engines 

 and tenders, were propelled successively past the zero or signal post, where the 

 propelling power was suddenly withdrawn, when the trains were allowed to run 

 freely forward until they stopped. 



The speeds at the zero post ranged from 27 to 42^ miles per hour. 



The distances run during the stop ranged from li to 3 miles. 



The Great-Northern train, weighing 199 tons, at 42i miles per hour, stopped in 

 a length of 15,189 feet ; the London and North-Western train, 188 tons at 42 miles 

 per hour, in 15,054 feet— giving a mean retarding force in those particular trains 

 of -35 per cent, of their weight, or about 8 lbs. per ton. 



The mean of the entire series gave a slightly higher figure. 



2. Friction of Engine and Tender. 



In like manner it was found that the friction of engine and tender coupled 

 together, no brakes being applied, amounted to -62 per cent, of their combined 

 weight, being about 14 lbs. per ton. 



Hence it may be assumed that the friction of a complete train (in which the 

 weight of engine and tender constitutes, say, one fourth of the gross weight of the 

 train), inclusive of the atmospheric resistance it encounters in its course, may be 

 taken at -42 per cent., being about 9| lbs. per ton. 



These results confirm what long experience would lead us to anticipate. 



3. Effect of Hand-Brakes. 



With the exception of a few passenger trains of some of the leading com- 

 panies, the bulk of the passenger traffic of the railways in this country had been 

 conveyed in trains possessing hand-brakes, one to the tender, and one to each van, 

 the former worked by the stoker, the latter by the guards. 



It thus became important, in the view of the Royal Commissioners, to ascortain 

 with precision what is the controlling power which these appliances afford._ 



The suitable trains were those furnished bv five of the Railway Companies, viz. 

 the London and North Western, the Caledonian, the Midland, the Great Northern, 

 and the London Brighton and South Coast, when it was found that the total mean 

 retarding force induced bv the application of hand-brakes to tender and to the two 

 vans amounted, inclusive of ordinary friction, to 2-30 per cent, of the gross weight ; 

 equivalent to encountering a gradient of 2-36 per cent., or 1 in 42. The mean 

 -ross weight of these trains, including engine and tender, was 220 tons, and their 

 mean speed at the time of cutting off steam was 47 1 miles per hour. _ 



The effect of such brakes was, in fact, such as that on a level railway a train 



