RAILWAY CONSTANTS. 245 



In the first experiment the velocity, commencing with 100 

 yards in nine seconds, was continually diminished to the foot of 

 the plane, where it was reduced to 100 yards in 238 seconds, 

 being at the rate of 12*6 feet per second, or 8*6 miles per hour. 

 At this speed, therefore, with a favourable wind, the resistance of 

 the carriage used in this experiment was greater than its gravity 

 down 1 in 178. In the second experiment the speed, com- 

 mencing at 100 yards in eight seconds, was gradually retarded 

 to the bottom of the plane, where it was reduced to 100 yards in 

 sixteen seconds, or 12*75 feet per second, being at the rate of 

 12*8 miles per hour. Since the retardation had not ceased, the 

 resistance of this carriage at the velocity of 18*8 miles per hour 

 must be greater than its gravity down 1 in 178. In the fourth 

 experiment, likewise, there is a continual retardation, com- 

 mencing at 100 yards in seven seconds. The velocity was gra- 

 dually diminished until, at the foot of the plane, it was reduced 

 to 100 yards in 17*2 seconds, being at the rate of 17'44 feet per 

 second, or 11'9 miles per hour, at which speed, therefore, the 

 resistance of the carriage used in this experiment was greater 

 than its gravity down 1 in 178. In the third experiment the 

 speed, commencing at 100 yards in seven seconds, was gradually 

 reduced, about the middle of the plane, to 100 yards in 12*8 

 seconds. Throughout the last 3000 yards the speed varied be- 

 tween 100 yards in 11*8 seconds, and 100 yards in thirteen 

 seconds, alternately increasing and decreasing, probably from 

 variations of the wind and the varying exposure on cuttings and 

 embankments, accompanied probably with slight changes in the 

 gradient. The speed may therefore be regarded as practically 

 imiform throughout this distance of 3000 yards, and its mean 

 value was 100 yards in 12*7 seconds, or 23*62 feet per second, 

 being at the rate of 16*6 miles per hour. 



The coach used for this third experiment was now taken to 

 the top of the plane and there dismissed with the speed of 100 

 yards in seven seconds, and it was determined to allow it to 

 move along the successive gradients until it should come to rest. 

 To observe the motion, the gradients were staked out in intervals 

 of 100 yards to a distance of 7200 yards beyond the foot of the 

 plane falling 1 in 178. The seventy-second stake was 275 

 yards short of the 53^ mile post, and the line beyond that was 

 divided by quarter- mile posts. The particulars of this experi- 

 ment are given in the following table. 



VOL. VII. 1838. 



