Book II. REPAIRING ROADS. 543 



3476. Farcy is of opinion, that six inch cylindrical wheels, or under, are the most 

 practicable an^ useful, provided the projecting nails are most rigidly prohibited, which 

 can never be done but by a penalty per nail upon the wheelers who put in tliose nails, 

 and upon the drivers of the carriages who use such roughly-nailed wheels. 



3477. Telford thinks that no waggon or cart wheel ought to be of less breadth than 

 four inches, and that in general no carriage ought to be allowed to carry more than at 

 the rate of one ton per wheel : " when it exceeds that weight," he says, " the best ma- 

 terials which can be procured for road-making, must be deranged and ground to 

 pieces." 



3478. Paterson is a warm advocate for broad wheels. " If the wheels were used 

 double the breadth as at present," he says, "they would act as rollers upon the materials, 

 binding them together, and consequently the surface would remain always smooth and 

 free from ruts ; and the waste or decay would, of course, be exceedingly little. All 

 broad wheels, however, should be made on a construction different from those that are in 

 ccommon use (Jig. 445 a.). Those in common use, 

 whether broad or narrow, are generally dished (as it 

 is called) on the outside, and the ends of the axle- 

 tree bent a little downwards. This causes the 

 wheels to run wider above than below; and the 

 reason, I believe, for adopting this plan was to 

 allow people to increase the breadth of their car- 

 riages, and yet the wheels to run in the same track. 

 Upon this plan, the edges of the wheel, to run flat 

 upon the road, must be of a conical shape, the outer edge being of a less diameter than 

 the inner one. Any bad effect arising from this is indeed very little felt from the 

 narrow wheels; but as they increase in breadth, the evil increases in the same proportion. 

 " A conical wheel," says Edgeworth, " if moved forwards by the axletree, must 

 partly roll and partly slide on the ground, for the smaller circumference could not 

 advance in one revolution as far as the larger. Suppose," says he, " the larger revolution 

 sixteen feet, and the smaller thirteen feet, the outer part must slide three feet, while the car- 

 riage advances sixteen, i. e. it must slide nearly one-fifth of the space through which the 

 carriage advances, thus, if loaded with ten tons, the horses would have two tons to drag, 

 as if that part of the weight was placed on a sledge. " The same thing has been ably and 

 beautifully demonstrated by Gumming [Essay on the Principles of Wheels and Wheel 

 Carriages, &c.}, and is very easily illustrated; take, for instance, the frustum of a cone, 

 or a sugar loaf from which you have broken off a little bit at the point ; then set this a 

 rolling upon a table, and instead of going straight forwards it will describe a circle ; and 

 if you will put a pin or axletree right through the centre of it, and upon that axle cause 

 it to move straight forwards, the smaller diameter must slide instead of rolling. It is 

 evident, therefore, that the rims of the wheels ought to be of a cylindrical form {b). 

 Edgeworth states, in relation to this, that " from the testimony given to the committee 

 of parliament, by every person of science and judgment, cylindrical wheels and straight 

 axletrees have been unequivocally preferred. 



3479. Farey finds the Whitechapel road more injured by broad wheels than any 

 other, owing to these wheels being barrelled and conical, and not running flat, and the 

 middle tier projecting above the others with rough nails. 



3480. Gumming has proved experimentally before the committee of 1 808, that when 

 the rim of a wheel is made truly cylindrical, so as to have an equal bearing on its 

 whole breadth, the resistance to its progress on a smooth road is not increased by increasin"- 

 its breadth. And in regard to the immense saving that would accrue to the nation, 

 Jessop, in his report, says, " I may venture to assert, that by the exclusive adoption of 

 cylindrical broad wheels and flat roads, there would be a saving of one horse in four, of 

 seventy-five per cent, in repairs of roads, fifty per cent, in the wear of tire, and that the 

 wheels with spokes alternately inclined, would be equally strong with conical ones, and 

 wear twice as long as wheels do now on the present roads." But, over and above the 

 preference due to such wheels, in respect to public roads, they are no less preferable when 

 applied to purposes of husbandry. Besides the great resistance to the draught occasioned 

 by the sinking of the narrow wheels on soft land, every farmer knows what injury is fre- 

 quently done to subsequent crops by such poaching and cutting up of the land. But 

 this is not all. Many a field of beautiful pasture, when subjected to the destroying 

 operation of the narrow wheels, is very much injured, both in respect to the appearance 

 and the crop, which would be entirely prevented by using broad wheels. Thus it has been 

 stated, in regard to the introductiorj of the use of broad wheels, that the saving on the 

 incidental repairs of the road would be immense ; that the roads would uniformly retain 

 a smooth and even surface, which would greatly contribute to the comfort of the traveller, 

 and the ease of the draught ; that in husbandry also the advantages would be great ; in 

 short, that in every point of view, the benefits that would be derived in consequence. 



