ON RAILWAY CONSTANTS. 26? 



Appendix a statement is given of the time occupied in performing the trips, 

 and of the time lost in stoppages, and in slackening and getting into speed 

 at the stations. The difference between the two shows the time which would 

 have been occupied if the train had started from Liverpool and Birmingham 

 at full speed, and travelled between those places without stopping. This 

 enables a comparison to be made between the mean speed on the level, and 

 the average speed maintained by the train from its departure from Liverpool 

 to its arrival at Liverpool again. An equal deduction for stoppages, and for 

 loss of time in getting up speed, would have been necessary, had the line of 

 road been level throughout. 



The mean speed on the level was 30'93 miles per hour. 



The time of performing the 190 miles, stoppages and delays deducted, ' 

 Avas 6 hours, 26 minutes, 48 seconds. 



If the 190 miles of road had been perfectly level, the time of performing 

 the journey would have been (at the rate of 30'93 miles per hour) 6 hours, 

 8 minutes, 54 seconds. 



In ordinary practice an engine of the dimensions of the Hecla would re- 

 ceive assistance up the Sutton, Whiston, and Warrington Incline Planes (1 

 in 89, 1 in 96, and 1 in 80). In the instance before us this was not the case, 

 and the train had the disadvantage of encountering gradients not contem- 

 plated in our theory ; whereby its speed sustained a loss not only in the 

 ascents but in the descents also, when the power of the brake was applied to 

 check the velocity. Taking all these attendant circumstances into account, 

 we may conclude that the opinion entertained by the Committee was a cor- 

 rect one, viz. that trains whose weight bore an ascertainable relation to the 

 nature of the gradients they had to traverse, could be made to traverse those 

 gradients at an average speed equal to what the power of the engine could 

 have accomplished on the level : that, for instance, a train of twelve carriages, 

 representing the size of an ordinary train of passengers on the Grand Junc- 

 tion Railway, v/ould travel over the existing gradients of that railway (saving 

 perhaps the steeper ones of 1 in 96, &c. just alluded to) in as short a time as 

 if the line had been absolutely level. 



On some lines of road a train of twelve carriages may be a less, and on 

 others a greater, than the average load which the conditions of traffic de- 

 mand. The power of the engine (meaning by that term its evaporative as 

 well as its tractive power) would then vary accordingly ; or if the line were 

 not already formed, the maximum gradient would be determined with refer- 

 ence to some standard form of engine, and to the probable size of the trains. 



In the account of the Hecla's performance a correct statement is given of 

 the fuel and water consumed on both trips. The average consumption of 

 fuel, it will be seen, amounted to the rate of 37 lbs. per mile, which is reckoned 

 on the entire quantity consumed during the day, including therefore all that 

 was used for raising steam in the morning, and for keeping steam up during 

 the intervals of rest. We shall not attempt to make an estimate of the duty 

 done by the unit of coke or water in transporting the load, because there 

 were no means of ascertaining the blast-pipe resistance, which it is believed 

 formed a very considerable portion of the whole resistance the engine had to 

 overcome, and because also later improvements in the locomotive engine 

 have been introduced, which enable them to perform an equal duty with at 

 least one-third less fuel. 



For the Committee of the British Association, 

 June 1841. Edwaud Woods. 



