ON DRAUGHT. 449 



In a rough road, therefore, the increased force with which the loao 

 would be thrown from side to side might prove very inconvenient and even 

 diuigerous, and would certainly be liable to increase the resistance when 

 the front-wlieels meet with any obstruction: but this it must be particu- 

 larly remembered 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. Secondly, 

 That there should be a firm, 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 elas- 

 ticity both upon the load and upon the wheels; and tliat the imj)ctus 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 with- 

 out 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 materials 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 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 ditrerent materials tc 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 *o 

 enter upon a mucli 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 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; tlieir 

 «;onstruction 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, at once to the question of roads. 



