266 



REPORT — 1841. 



Now, as by the hypotliesis the terminal points of the railway "are on a level 

 with each other, the sum of tlie descents must be equal to the sum of the 

 ascents. On the descents the force of gravity is brought into co-operation 

 with the power exerted by the engine, and a speed would hence result greater 

 than the speed which could be accomplished on the level. Although the 

 Committee were fully aware that resistance increased in a greater ratio than 

 speed, occasioning thereby some extra absorption of power on the descend- 

 ing gradients in making up for loss of time on the ascending ones, they were 

 nevertheless strongly impressed by the consideration of this principle of 

 compensation, and were of opinion that the loss of time on the whole 

 journey would be but trifling, provided the gradients were not very unfa- 

 vourable. To ascertain the value of this opinion, an experiment was made 

 with the Hecla engine, tender, and a train of twelve carriages, weighing al- 

 together 82 tons ; and every precaution was used to obtain accuracy in the 

 observation of velocity, consumption of fuel, and evaporation of water. The 

 line chosen was the Grand Junction and part of the Liverpool and Man- 

 chester Railway. The point of departure was Liverpool, and the train was 

 conveyed from thence to Birmingham and back, a total distance of 190 miles. 

 The point of termination of the journey was therefore Liverpool, the train 

 being brought again to the same level after traversing a long series of undu- 

 lations. 



The Table in the Appendix exhibits the time of passing the different 

 quarter mile-posts, taken by a stop watch ; also the variations in the inclina- 

 tions of the road ; the difference of time between the quarter mile-posts and 

 the average speeds, as well as the particulars of stoppages for coke and 

 water at the stations. 



Collecting into one table the uniform speeds observed, both in ascending 

 and descending the several gradients, and comparing the mean of these 

 speeds with the average speed actually accomplished on the level portion 

 (4 miles in length) northward of Crewe Station, we find an extraordinary 

 coincidence in the results. The uniform rate of speed on the level was 

 30'71 miles per hour on the up-journey, 31*15 miles per hour on the down- 

 journey ; and the mean of the two is 30*93 miles per hour. 



The remarkable inference to be drawn from this table is, that a train of 

 twelve carriages, drawn by the same engine, can be conveyed over a railway 

 whose gradients range within the limits specified in the above Table, in the 

 same time as it could over a perfectly level railway of equal length. In the 



