370 HIGHWAYS AND HORSES. 



complete circle by means of steam ; wheels made in this 

 way are preferable in appearance, but the difficulty 

 of repairing them has prevented their being brought 

 into general use. The external surface of the felloes 

 is protected by a covering of iron called the tire. The 

 spokes standing at right angles with the axle are 

 adapted to meet the lateral shocks to which a carriage- 

 wheel is exposed. The spokes are usually formed of 

 oak saplings and are wrought into proper form after 

 being driven into the nave ; the nave is protected at 

 either end by this hoop of iron called the tire, to 

 enable it to resist the strains of the spokes. In 

 ordinary hind coach-wheels there are generally four- 

 teen spokes, and in the fore-wheels, which are about a 

 foot lower, there are usually only twelve spokes. 



The tire is put on the wheel when expanded by 

 heat, but as soon as the iron hoop is fitted into its 

 proper place round the wheel, water is thrown upon 

 it to prevent the wood-work from catching fire, and 

 the result of the sudden contraction of the hoop or 

 tire is to compress the felloes and to force each spoke 

 into its proper place, so that when complete, the wheel 

 is admirably adapted by its combined strength and 

 elasticity for the purpose for which it is designed. 

 The tire is further secured, after cooling, by a few small 

 bolts driven through it and the felloes, and riveted 

 inside the latter. 



But to speak once more of timber employed in 

 coach-building. Mahogany is chiefly in request for 

 forming the panels or broad plain surfaces of the body 

 of a coach ; it always seems a great pity that such a 

 beautiful wood as mahogany should be concealed by 

 paint. It is a mere question of fashion and habit. We 

 have grown so accustomed to painted carriages that 



