218 



REPORT— 1841. 



On comparing the general results of this experiment with those of the same 

 train in its ordinary state,we obtain the following comparative table of effects. 



These results prove that the open spaces between the coaches have no 

 effect on the resistance. 



On comparing the preceding experiments with those made with a train of 

 waggons having high sides and ends capable of being taken down and laid flat 

 upon them, it will be seen that although a change of frontage produce no ob- 

 servable effect on the resistance, a change in the entire volume or bulk of the 

 train produces a very considerable effect on the resistance to the tractive power. 



If that part of the resistance due to the a,ir depend altogether, or chiefly, 

 on the frontage of the train, it would follow that by increasing the extent of 

 the train by additional coaches, that part of the resistance would receive 

 either no augmentation, or would be inconsiderably increased. To reduce 

 this to the test of experiment, it was accordingly determined to run trains of 

 various magnitude down inclined planes till they should attain uniform velo- 

 cities, and thereby discover the manner in which their resistance would be 

 affected. 



Experiments of this kind having been already made with trains of four 

 coaches, and reported in the former part of this paper, it was now resolved 

 to extend them to trains of six and eight coaches. The following are the 

 results of these experiments, which in their details were conducted in all re- 

 spects in the same manner as before. 



