238 EIGHTH REPORT — 1838. 



periments down the Whiston plane, and from those of M. de 

 Pambour on the Sutton plane. 



In considering these experiments, and in deducing from them 

 any inferences of a genei-al nature, it is of importance to re- 

 member that in all of them a wind of unascertained force blew 

 up the planes, and therefore against the motion of the train. 



It may be observed that in these experiments no perceptible 

 effect is produced by the curves. The uniform velocity of the 

 train in the second experiment is the same before entering on 

 the curve which commences at the I7th stake on the gradient of 

 1 in 178, and after passing the 5tli stake, where the line becomes 

 straight. 



From all these experiments it is apparent that a train of rail- 

 way cai-riages in descending an inclined plane is subject to a re- 

 sistance which is continually augmented as its motion is acce- 

 lerated, and that if the plane have sufficient length, this resist- 

 ance will at some certain speed become equal to the gravitation 

 down the plane, and then all further acceleration must cease. 

 This conclusion will be corroborated, and indeed put beyond all 

 doubt by other experiments which are still to be reported. It 

 will be evident, therefore, that if the train on Avhich the experi- 

 ments were made be started from a point at a sufficient distance 

 from the foot of the plane, the velocity which it will have when 

 it leaves the foot of the plane and commences to move along the 

 next gradient will be the same, whatever maybe the point from 

 which it may have been started. 



Let A B be the inclined plane down which the train is moved, 

 and let B C be the succeeding gradient. Let S be a point 



from which the train being started it will acquire the uniform 

 speed before it arrives at B. Then, if it be successively started 

 from S', S", or any other point still more distant from B, it will 

 have, on arriving at B, the same velocity. It will, therefore, in 

 all cases move on B C to the same point before it be brought to 

 rest. Let this point be R. 



According, then, to the method of determining the resistance 

 adopted by M. de Pambour (p. 199.), the amount of resistance 

 obtained when the train is started from S would be equal to the 

 gravity on the inclination S R ; if started from S', it would be 

 equal to the gravity on the steeper plane S' R ; if started from 



i 



