RAILWAY CONSTANTS. 241 



of the plane, and subsequently a very slight increase. These 

 fluctuations were, however, so small that they may fairly be 

 attributed to the varying effects of the wind arising from the 

 different exposm-e of the train in cuttings and on embankments. 

 The velocity, therefore, may be regarded for nearly 5000 yards 

 as practically uniform, the mean rate in the first experiment 

 being 100 yards in 9'74 seconds, or 30*8 feet per second, which 

 is equivalent to twenty-one miles per hour ; and in the second 

 experiment 100 yards in 9"95 seconds, or 31'6 feet per second, 

 being 21| miles per hour. The mean of the two will give a ve- 

 locity of 51*2 feet per second, or 21;^ miles per hour. Hence it 

 appears that the resistance of this coach train, at a velocity of 

 21| miles an hour, is the l78th part of its weight, or 226*8 

 pounds, being at the rate of 12*6 pounds per ton of the gross 

 weight. 



In the third experiment made with the first-class carriage 

 and one second-class carriage coupled, the speed commencing 

 from the summit was 100 yards in fourteen seconds, which was 

 gradually diminished to a point beyond the middle of the plane, 

 where it was reduced to 100 yards in sixteen seconds. It then 

 slightly increased to 100 yards in thirteen seconds, which was 

 maintained uniform for the last 1000 yards. In the fourth ex- 

 periment with the second-class carriages, the initial velocity 

 at the top of the plane was 100 yards in twelve seconds, which 

 was gradually diminished,till at the middle of the plane the ve- 

 locity was 100 yards in 172 seconds, after which it was gradually 

 but slightly increased to the foot of the plane, where the final 

 velocity was the same as in the third experiment. Considering 

 the lightness of the trains and the consequently increased efl"ect 

 of the wind, these fluctuations of speed probably arose from the 

 varying shelter and exposure of cuttings and embankments in 

 the descent. In the third experiment the mean velocity through 

 5000 yards was 100 yards in 14'7 seconds, or 20*4 feet per se- 

 cond, being at the rate of 13-91 miles per hour. In the fourth 

 experiment it was at the rate of 100 yards in 15*16 seconds, or 

 ] 9'8 feet per second, being at the rate of 13*5 miles per hour. The 

 mean of these two is 20" 1 feet per second, or 13-7 miles per hour, 



Now it follows that, the wind being with it, this train of two 

 coaches suffered a resistance, the total amount of which, at 13'7 

 miles per hour, amounted to the l7Sth part of their gross weight, 

 or to 113-4 pounds. 



The train of four coaches after having descended the plane 

 falling 1 in 178, as described in the first two of the preceding 

 experiments, was allowed to continue its motion on the succeed- 

 ing plane, falling at the mean rate of 1 in 266, and extending to 

 a distance of 5360 yards from the foot of the former plane. 

 The particulars of these experiments are given in the following 

 table. 



