Observations upon Wheel- Carriage Experiments. 25 1 



and their cumbrous appurtenances are more than ten times 

 heavier than they should he, in proportion to their wheels and 

 axles ; an inconsistence sufficient to destroy the useful effect of 

 any experiment. The body of the common cart or dray, used 

 in the last of these experiments, is not the one-third of the 

 weight of its wheels and axle; whereas these deceptive bodies, 

 as prepared, are above three times heavier than their wheels and 

 axles — Here is a disparity in proportion of above ten to one. 

 For the sake of illustration, and to enaljle me to draw reasonably 

 any conclusion from this experiment, I shall consider all weight 

 beyond that of the common dray as so much loading on both of 

 these peculiar carriages, unsuitably chosen, where the advantage 

 by use of springs was to be estimated in proportion to the weight 

 drawn. It will appear agreeably to my subsequent calculation, 

 that at the time these carriages were supposed by Mr. Edge- 

 worth to be empty carriages, and perfectly similar, they were in 

 reality loaded carriages, of different weights, of different burden, 

 and differing essentially in construction. It will appear, that 

 the previous loading, consisting of the unnecessary weight of 

 Ijody and weights called equalizing weights, of the one was 

 ^, cwt. 1 qr. 23 lbs. to which five hundred weight was added, and 

 called its loading, together making 10 cwt. 1 qr. 23 lbs. and the 

 previous loading of the other was 5 cwt. qrs. 13 lbs. to which 

 was subsequently added, under the denomination of loading, 

 Hcwt. 1 i\T. 01b. making together 11 cwt. I qr. 13 lbs. exhibiting 

 a difference of 3 qrs. 18 lbs. 



These carriages being supported in front by men, during the 

 experiment, renders the result very uncertain. 



It was observable that their metal loading was not confined ; 

 there might therefore be much weight, to be supported by the 

 men in front of one, and much force of a contraiy nature, to be 

 overcome by the men, in front of the other, as in the instance of 

 the shafts of one of these carts raising two men many feet from the 

 ground, during its progress ; weights for such a ])urposc should 

 be so fixed as to be unalterable by the motion of the carriages. 



The axles of the carts in ([uestion were conical ; tlieir apexes 

 or extremities were set much below a line horizontal with their 

 bases respectively. 



Mr. Edgeworth in his work upon Roads and Wheel Carriages, 

 page 7'i, describing the nature of a conical axle bended down- 

 wards, savs, " Whoever has observed the hinder wheels of a car- 

 riage, that has the axle nmch bent downwards, will perceive a 

 tremulous motion of the whole wheel, wiiich arises from its truly 

 circular motion being counteracted by the conical motion, to 

 whicli it is disposed by the bended axletrce." — I am not aware 

 pi what is meant here by the conical motion of the wheel ; the 



proper 



