5G0 



OX DRAUGHT. 



lig. 31. 



suppose that the outer surface of the tires should be cyhndrical, as it is 

 the onlj form which admits of the wheel rolling freely in a straight line ; 

 but it is nevertheless the form of this surface, its breadth, and the degree 

 of dishing which have varied so much from the causes before mentioned, 

 viz. the state of the roads, and to the consideration of which we will now 

 return. 



A road, however inuch neglected and out of repair, will generally have, 

 at a certain depth, a hard bottom ; above this will be a coat of mud or loose 

 stuff, more or less deep, according to the material used, and the frequency 

 of repair or the quantity of wet to which it may be exposed. It is sinking 

 through this, until it reaches the hard bottom, that causes the resistance to 

 the j)rogress of the wheel : Avhether the wheel be wide or narrow, it must 

 squeeze or grind its way to the bottom of this mud ; a narrow wheel evi- 

 dently displaces less, and therefore offers less resistance. The great object 

 of carriers, then, was very naturally to place as great a load as they could 

 upon wheels which were as narrow as possible, consistent with the 

 necessary strength. 



It was soon perceived that the entire destruction of the roads would be 

 the consequence of this system, Avhich had its origin in the bad state of the 

 roads. A certain width of tire proportionate to the load was therefore 

 required by law. The endeavour to evade this law was the cause of the 

 absurd form of Avheel we are about to describe and to condemn. 



In apparent obedience to the law, the felloes of the wheels were made of 

 an excessive breadth ; but to retain the advan- 

 tages of the narrow wheel, the middle tire was 

 made to project so far beyond the others (see 

 ^^^g. 31,) that it in fact constituted the wheel, 

 the others being added merely to give a nominal, 

 and not a real width. The enormous loads 

 which it was found advantageous to place on 

 these wheels rendered it necessary to give them 

 a considerable degree of dishing, to resist lateral 

 shocks, and, besides, the carriers were by this 

 means enabled to give a great width of floor to 

 the carriage, still keeping the vehicle in the common tracts or ruts, so that 

 the wheels ultimately assumed theform represented, _%. 32. 



If such a machine had been constructed for the express purpose of grind- 

 ing the materials of the road to powder, or of serving as a check or drag 

 to the waggon, it might, indeed, have been judicious, but as a wheel it was 

 monstrous. Yet this is the form of wheel upon Avhich the contradictory 

 opinions referred to in the first page of this treatise were given before a 

 Committee of the House of Commons. A carrier of Exeter was in favour 



of these wheels, and in support of his opinion, 

 adopts them to this day. But a few days ago 

 we saw one of his waggons with wheels, 

 which, although only about twelve inches 

 Avide, were six inches smaller at the outside 

 than at the inside. Such a cone, if set rolling 

 and left to itself, would run round in a circle 

 of little more than twenty feet diameter. 

 What must be the grinding and the friction, 

 then, when it is constantly compelled to go on 

 in a straight line? yet enough has been Avi-itten 

 and said upon this subject to convince, we 

 should imagine, the most prejudiced of the 

 absurdity of the sj^stem. 



