214 EIGHTH REPORT 1838. 



had been however to an equal extent neglecfed, so far as we are 

 informed, by engineers generally, and indeed by all who had 

 directed their attention to the practical working of railways and 

 to the experimental investigation of their effects. Some scien- 

 tific men had called the attention of engineers to the subject, 

 and Mr. Herapath more especially insisted on its importance, 

 made various calculations of its probable effects, and predicted 

 that on railways worked at higl\ speeds it would prove to be the 

 chief source of resistance to the moving power. As, how- 

 ever, no direct experiments had been made to demonstrate its 

 amount, and as it was known that the theory of the resistance 

 of elastic fluids had not been based on experiments with suf- 

 ficient certainty and precision to render its principles capable 

 of being applied for practical purposes in operations of the kind 

 now considered, these suggestions were disregarded, and the 

 effects of the resistance of the air continued to be considered 

 as sufficiently allowed for by estimating them in combination 

 with friction at mean speeds, no attempt whatever having been 

 made to ascertain experimentally the variation of resistance of 

 the same loads at different speeds. 



It was determined, in the first instance, to repeat and vary 

 the experiments on the accelerated motion of trains down in- 

 clined planes, and their retarded motion in running to rest 

 where the resistance exceeded the moving power. 



The first experiments made with this view were tried on the 

 same inclined plane on which the experiments of M. de Pam- 

 bour were made, viz. the Sutton plane on the Liverpool and 

 Manchester Railway. This plane and the level at its foot were 

 staked out as in M. de Pambour's experiments, but in the pre- 

 sent case the tiine of passing each successive stake was observed 

 and recorded, so that the variation of speed, during the motion, 

 might be rendered apparent. 



In these experiments it became manifest, that the rate of ac- 

 celeration in the descent and the subsequent retardation could 

 not be represented by the formulae for uniformly accelerating 

 and retarding forces, and that therefore some force was in ope- 

 ration which, milike friction, had a dependence on the velocity. 



To decide this, it was determined to try the effect of gravity 

 on a train of loaded wagons descending an inclined plane less 

 steep than those which occur upon the Liverpool and Man- 

 chester Railway, and for that purpose the Madeley plane on the 

 Grand Junction Railway, already mentioned, was selected, and, 

 as a first trial, a train of wagons loaded with iron rails and 

 chairs was prepared. This train was placed near the summit 

 of the plane, and was allowed to move down by gravity. The 



