ON DRAUGHT; 449 



In a rouo-h road> the increased force with which the load would be 

 thrown froni side to side might prove very inconvenient, and even danger- 

 ous, and would certainly be liable to increase the resistance when the front 

 wheels meet with any obstruction : but this it must be particularly remem- 

 bered is only true in the case of slow velocities and carriages without 

 springs. 



We have now considered in succession the various parts of the vehicle 

 for conveying the weight, and shown in what manner they affect the 

 draught, and how they should be constructed so as to diminish as much 

 as possible the amount of this draught. We have endeavoured to 

 point out the advantages and necessity of attending to the construction and 

 size of the wheel. Thus it should be as nearly cylindrical and vertical as 

 possible, and of as large a diameter as can conveniently be admitted. 

 2dly, That there should be a iirm, unyielding connexion in the direction of 

 the movement between the power employed, the weight moved, and the 

 wheels: in other words, that the force should always act directly and 

 without elasticity both upon the load and upon the wheels ; and that the 

 impetus or momentum of the load, when in movement, should always act 

 in the same manner, without elasticity in propelling the wheels ; — and 

 lastly, that it is highly advantageous to interpose as much elasticity as 

 possible by means of springs in a vertical direction between the wheels and 

 the body, so that the former may rise and fall over stones or irregularities 

 in the road without communicating any sudden shocks to the load ; and 

 we believe that the proper application of springs in all cases, even with the 

 heaviest loads, would be found productive of great good effect. 



Attention to those points will tend to diminish 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 unfor- 

 tunately least affected by any of those arrangements. We allude to those 

 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 propor- 

 tion 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 increasing the 

 diameter of the wheel even will be of very slight assistance; 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 sub- 

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

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

 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, dependant 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 requn-ed for the 

 proper consideration of the subject of draught by animal power. The 

 requisites for a good road is all that we shall indicate. 



Channel of conveyance, in a general point of view, must include canals, 

 roads, and railways. Of the first, however, we shall say little; then' 

 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. ^ _ 



2 U 



