OF WHEEL-CARRIAGES. 97 



lives of their workmen, that excepting the late Sir LECT 

 James Creed of Greenwich, and some gentlemen at^^i^, 

 Bristol, there is scarcely an instance of any who has 

 used this safe contrivance.* 



The structure of wheel-carriages is generally so well Wheel- 



comages, 



known, that it would be needless to describe them. 

 And therefore, we shall only point out some incon- 

 veniences attending the common method of placing the 

 wheels, and loading the wagons. 



In coaches, and all other four-wheeled carriages, the 

 fore-wheels are made of a less size than the hind ones, 

 both on account of turning short, and to avoid cutting 

 the braces : otherwise the carriage would go much 

 easier if the fore-wheels were as high as the hind ones, 

 and the higher the better, because they would sink to 

 less depths in little hollowings in the roads, and be the 

 more easily drav n out of them. But carriers and coach- 

 men give another reason for making the fore-wheels 

 much lower than the hind-wheels ; namely, that when 

 they are so, the hind-wheels help to push on the fore 

 ones: which is too unphilosophical and absurd to deserve 

 a refutation, and yet for their satisfaction we shall shew 

 by experiment that it has no existence but in their own 

 imaginations. 



It is plain that the small wheels must turn as much 

 oftener round than the great ones, as their circum- 

 ferences are less. And therefore, when the carriage is 

 loaded equally heavy on both axles, the fore-axle must 



Note 39. The cranes described by our author are still very generally 

 employed, although others of a more improved form have, in some cases, 

 been substituted. One of which will be shewn in a subsequent page. 

 An expanding wheel crane has been recommended by the Society of 

 Arts, who have rewarded its ingenious inventor ; but when ordinary 

 weights are to be raised, the labourers to whom these engines are gene- 

 rally entrusted, appear to prefer the more obvious arrangement of 

 wheels and pinions, by means of which the same mechanical advantage 

 is attained. 



H 



