252 



REPORT — 1841. 



stance, the time of descent through the same space was 4™ 5P, indicating a 

 slightly increased amount of friction. It is not thought necessary to enter 

 into a calculation of their friction on the 8th July, inasinuch as the perform- 

 ances agree very closely; and with the view of comparison with other sets of 

 experiments made on the same day, it is considered on the whole fairer to 

 ascertain the friction on that day, viz. the 12th July. 



Five computations are made from observations of the times of descent 



from No. to No. 5 post. 



tons. 



The weight of the train, exclusive of wheels and axles, was S^'OS 



The weight subject to rolling motion, viz. the wheels and axles, was 6*40 



Total .... 40-45 

 The radius of the wheels was 18 inches, and the distance from the centre 

 of the wheel to the centre of oscillation, 10 inches. In accordance with these 

 data, the coefficient of correction for the quotient alluded to, page 249, is 1'088. 



Eight Grand Junction Carriages = 40'45 tons. 



Here, as before, we find the friction diminishes, it being least when the speed 

 averages 5*84 miles per hour. From both series of experiments we deduce 

 the following conclusions, which will be adopted in the subsequent investiga- 

 tions : — 



1. The friction was least when the train was moving at the rate of about 

 6 miles per hour. 



2. The total resistance of the train was also least when moving at about 6 

 miles per hour, notwithstanding the effect of the atmosphere at that speed. 



3. The mean resistance of the Liverpool and Manchester carriages was 

 never less than 5-60 lbs. per ton. 



-i. The mean resistance of the Grand Junction carriages was never less 

 than 7*75 lbs. per ton. 



We shall call the friction of the Liverpool and Manchester carriages equal 

 to 6 lbs. per ton, and that of the Grand Junction carriages equal to 8 lbs. per 

 ton, numbers which represent nearly the mean of the computed measures of 

 friction. 



2. The second point of our inquiry is now to be considered, viz. the effect 

 which accompanies an increased speed of the train, as regards the amount of 

 resistance experienced. We shall first present an analysis of the experiments 

 made on the Sutton plane when the air was perfectly calm. Some of these 

 experiments have been before noticed and made use of for determining the 

 friction of the trains, but all will be found detailed in the Tables numbered 

 IV., v., VIL, VIIL 



To begin wij;h the train of three Liverpool and Manchester carriages, which 

 descended the Sutton plane on the 23rd August, 1839 (see Table, No. IV.). 

 The weight and other particulars have been stated before. The train having 

 acquired considerable speed, was observed to pass posts Nos. 5, 10 and 15, at 



