RAILWAY CONSTANTS. 243 



In the first experiment the train moved over this gradient 

 with a gradual retarded motion, commencing with the velocity 

 with which it left the former plane, and gradually diminishing 

 in speed until it attained the rate of 100 yards in 16*36 seconds, 

 with which speed it passed on to the succeeding gradient. In 

 the second experiment the train, in like manner, was retarded 

 till it attained the velocity of 100 yards in 14-32 seconds, with 

 which it passed to the succeeding gradient. The difference be- 

 tween the final velocities in descending this gradient in the two 

 experiments must be ascribed to the varying force of the wind, 

 since the train in both was the same, and the initial velocity 

 was not materially different. The mean of the two final velo- 

 cities is 100 yards in 15*34 seconds, or 19*55 feet per second, 

 being at the rate of 13*3 miles per hour. 



Since, then, this train in descending the gradient 1 in 266 had 

 not yet ceased to be retarded, having attained the velocity of 

 19*55 feet per second, it follows that at this velocity the resist- 

 ance to the train must have exceeded its gravity down that 

 gradient. 



It was now determined to try the effects of four carriages 

 moved separately down the inclined plane falling 1 in 178. The 

 carriages were therefore separately puslied to the summit of the 

 plane and dismissed from it at a higli speed, the times of pass- 

 ing the successive posts being observed as in the former case. 

 The results of these four experiments are exhibited in the follow- 

 ing table. 



