ON DRAUGHT. 561 



Attention to these points will tend to dimmish considerably the amount of 

 draught. As far as regards friction at the axles, and the resistance in passing 

 over obstacles in the road, it will assist the favourable application of the force 

 of traction when obtained from animal power; but that which we have shown 

 to be the most considerable source of resistance is unfortunately least affected by 

 any pf those arrangements. We allude to the resistance arising from the yielding 

 or crushing of the material of the road : we have seen that on a good turnpike-road 

 the draught was increased in the proportion of thirty to forty, or about one- 

 third, by the road being slightly dirty ; and that, on a heavy, sandy road, the 

 draught was increased to 205, or nearly seven times. Springs will not affect 

 this; and even increasing the diameter of the wheel will be of very slight assist- 

 ance ; nothing but removing at once the prime source of this evil, improving 

 the roads, can remedy this. We are thus naturally led to the third division of 

 our subject, viz., the road or channel of conveyance. In considering this as a 

 branch of the subject of draught by animal power, we shall merely point out 

 what are the principal desiderata in the formation of a good road, and what are 

 the evils principally to be avoided. To enter into all the details of their 

 construction, dependent as it is on the different materials to be found in the 

 neighbourhood, their comparative cost, the quality of the ground over which 

 the road is made, and many other points, would be to enter upon a much more 

 extensive field than is at all required for the proper consideration of the subject 

 of draught by animal power. The requisites for a good road are all that we shall 

 indicate. 



Channel of conveyance, in a general point of view, would include canals, roads, 

 and railways. Of the first, however, we shall say little ; their construction does 

 not materially affect the amount of draught, and we have already examined the 

 mode of applying the power, and the quantity of effect produced : we shall 

 proceed therefore at once to the question of roads. 



The inquiry into the best form and construction of wheel carnages has taught 

 us what we might indeed have foreseen, that perfection in a road would be a 

 plain, level, hard surface : to have learned this only would not have advanced us 

 much, as such perfection is unattainable; but we have learned also the comparative 

 advantages of these different qualities of hardness, smoothness, and level. We 

 have come to the conclusion, that slight alterations of level which shall vary the 

 exertion required of the animal, without at any time causing excessive fatigue, 

 are rather advantageous for the full development of his power than otherwise ; 

 that the inconvenience of roughness is obviated by the use of springs ; and 

 that even when the ordinary carts and waggons without springs are used, 

 still the resistance arising from mere unevenness of surface, when not excessive, 

 is not nearly so great as that which is caused by the yielding of the substance 

 of the road. Hardness, therefore, and consequently the absence of dust 

 and dirt, which is easily crushed or displaced, is the great desideratum in 

 roads. 



To satisfy this condition, however, smoothness is to a certain degree requisite, 

 as the prominent parts would be always subject to abrasion and destruction : for 

 the same reason, even if for no other, ruts and every thing which can tend to 

 form them must be avoided. 



A road should, in its transverse section, be nearly flat. A great curvature or 

 barrel, as it is termed, is useless ; for the only object can be to drain the water 

 from it : but if there are ruts, or hollow places, no practicable curvature will 

 effect this; and if the road is hard and smooth, a very slight inclination is.sufn- 

 cient. Indeed, an excess of curvature is not only useless with the present 

 construction of carriages, but facilitates the destruction of the road ; for there 

 are few wheels perfectly cylindrical : yet these, when running on a barrelled or 



