ON RAILWAY CONSTANTS. 



253 



the respective velocities of 27"50 feet, S^-TS feet, and 41*2,5 feet per second, 

 the velocity having evidently been accelerated throughout. Three compu- 

 tations have been made from these data, in connection with the time occu- 

 pied in traversing the distances between the posts, distances equal to 1650 

 feet in each case. The mean resistance having been computed, the mean ve- 

 locity (found by dividing the distance in feet by the number of seconds oc- 

 cupied in passing over) is placed opposite in the table, and it is to this mean 

 velocity that the resistance is presumed to refer. 



Three Liverpool and Manchester Carriages = 14"8 tons. 



The friction of the train of eight Grand Junction carriages was determined 

 from an experiment on the Sutton incline (Table, No. V.). The resistance 

 at higher speeds may be deduced from the same experiment. In this resist- 

 ance, as in the case of the Liverpool and Manchester train, the carriages 

 started from a state of rest, at No. post, and were accelerated to the foot of 

 the plane. 



Eight Grand Junction Carriages = 40*4<5 tons. 



Bearing in mind that the friction of the two sets of carriages were respect- 

 ively determined to be 6 and 8 lbs. per ton, it will be seen how considerably 

 the resistance has augmented with the speed. The resistance experienced by 

 the train of three carriages, when moving at 22'5 miles per hour, became 8'22 

 lbs. per ton; when at 26'16 miles per hour, 12"07lbs. per ton ; and when at 

 29*6 miles per hour, 16"26 lbs. per ton, or finally, more thautdouble the re- 

 sistance at 6 miles per hour. The resistance encountered by the train of 

 eight carriages, when moving at 20*54 miles per hour, became 11 'SI lbs.; 

 when at 25*86 miles, 12*25 lbs.; and when at 29*61 miles per hour, 14*65 lbs. 

 Here the ratio of the increase was less, owing to the greater weight of the 

 train. 



On the same evening, the 12th July, two other experiments were made 

 with portions of the same train of cai'riages. A train of four carriages was 

 provided, and after that a train of six carriages. These trains, instead of being 

 allowed to descend quietly from the top of the plane, were impelled over the 

 summit at the speeds of 33 and 26 miles per hour, by means of a locomotive 



