RAILWAY CONSTANTS. 239 



S", it would be equal to the gravity on the plane S" R ; and, in a 

 word, the value of the resistance according to this method might 

 be found to be of any amount whatever. 



The experiments were next directed to the trial of the move- 

 ment of trains of coaches down the series of planes extending 

 from Madeley to Crewe, already described, and were conducted 

 by Dr. Lardner. A train consisting of one first-class and three 

 second-class close coaches, were loaded in the same manner as 

 the train of first-class coaches used in the experiments already 

 described upon the Whiston plane, the gross weight being 18 

 tons. The second-class coaches differed in nothing but the 

 structure of their body from the first chiss, their transverse sec- 

 tion being nearly the same. In addition to the fifty-seven stakes 

 by which the plane falling 1 in 178 had been divided, a fifty- 

 eighth stake was placed at the top of the plane, the inclination 

 being found to extend 100 yards higher than fifty-seventh stake. 

 The direction of the line was nearly due north and south, and 

 the wind was from the south, and therefore blowing directly 

 down the plane. No means of ascertaining its velocity could 

 be procured at the time. The train was in each case pushed by 

 an engine to the fifty-eighth stake, and there dismissed to de- 

 scend the plane by gravity. The time of passing the successive 

 stakes was observed as in the former experiments. In the first 

 two experiments, given in the following table, the entire train 

 was dismissed down the plane, the carriages being coupled 

 by Mr. Booth's patent couplings. In the third experiment the 

 first-class carriage and one of the second-class carriages, coupled, 

 were used ; and in the fourth experiment the other two second- 

 class carriages. The entire transverse section of the carriages, 

 including the frame, wheels, and axles, was 61 square feet, and 

 the distance between carriage and carriage, when coupled by the 

 patent couplings, was 3 feet 10 inches. 



