38o HIGHWAYS AND HORSES. 



fact, a lever where the power is made to act continu- 

 ously ; by the revolving of the wheel, a number of 

 levers of the first class are continually brought into 

 motion ; as the radius of the wheel exceeds that of the 

 axle so it increases in power, and so increases the dis- 

 tance that the operative force has to pass through. A 

 large wheel, when set in motion, exercises a centrifugal 

 force, the axle being the basis of its operations, and 

 the tendency to the motion described being increased 

 with the diameter of the wheel. 



Several attempts have been made to provide high 

 wheels for the fore body of a four-wheel carriage as 

 well as for the hind body, but the difficulty has been 

 to lock the carriage round. In a four-wheel carriage 

 there is an axle connecting the two fore wheels, and 

 another connecting the two hind wheels, but if these 

 two axles were so fixed as to remain constantly parallel 

 the carriage could not turn. In practice the front 

 axle is made to turn upon a pivot, and the wheels 

 connecting it are made small enough to go under the 

 frame of the carriage during the act of turning. It 

 is for this reason, and this alone, that the front wheels 

 are made smaller than the hind ones, and as a great 

 disadvantage in draught is thereby occasioned, various 

 contrivances have been adopted for rendering the use 

 of somewhat larger wheels practicable. 



Sometimes the body of the carriage is raised to 

 a greater height ; sometimes a portion of the under 

 part of the body is cut away to leave room for the 

 turning of the wheel. It was as a means of remedying 

 these inconveniences, that Mr. Adams proposed, a few 

 years ago, the " sequirotal " construction of carriages, 

 of which I will afterwards speak more fully. 



As the inequality in the sizes of the fore and hind 

 wheels is adopted solely as a means of enabling the 



