RAILWAY CONSTANTS. 



237 



In the third experiment, in whicli the end surface was dimi- 

 nished, the train attained an uniform velocity at the 10th 

 stake of 100 yards in 10^ seconds, or 28-6 feet per second, 

 or 19^ miles an hour, whicii it preserved to the foot of the 

 plane. The resistance, therefore, at this speed with the dimi- 

 nished end surface was 8*5 lbs. per ton, and the total resistance 

 was 255 lbs. 



It appears, therefore, that with the frontage of 47' 8 square 

 feet this train suffered a greater resistance at 8^ miles an hour, 

 than that which it sustained with the lesser frontage of 23-8 

 square feet at 19^ miles an hour. 



In the second and third experiments the train continued to 

 move on the succeeding gradients, and the circumstances of its 

 motion are exhibited in the following table. The gradient of 

 1 in 330 and the succeeding level are straight. 



It appears, therefore, that with the greater frontage the train 

 came to rest after having proceeded half a mile on the gradient 

 of 1 in 330. With the diminished surface the motion was gradu- 

 ally reduced to the foot of the gradient of 1 in 330, the average 

 epeed on the last quarter of a mile of that gradient being 109 

 yards in 72'5, or 4*14 feet per second, being nearly three miles 

 an hour. It may therefore be inferred that with the lesser sur- 

 face, at very slow rates of motion, the resistance was somewhat 

 gi'eater than the gravity down an inclination of 1 in 330. This 

 resistance is at the rate of 6*8 lbs per ton, and the total resist- 

 ance for the train of 30 tons was therefore greater than 204 lbs. 



It may be observed that this result is quite in accordance 

 with those already obtained in p. 21 1 and p. 231, from the ex- 



