401 ON DRAUGHT. 



the tlrauglit in the proportion of four to five; while it was stated by the 

 other, who had also made the experiment on a large scale, that he found 

 tiiey materially assisted in keeping the roads in repair, and diminished the 

 draught in the proportion of five to four. 



Amidst such conflicting and contradictory opinions, it would appear 

 difficult to come to any useful conclusion, and we might naturally be dis- 

 posed to adopt a very common practice, that of taking an average result. 



A little consideration, however, will show that these apparent discrepan- 

 cies and contradictions arise, in great measure, from attempting to gener- 

 alise and apply to practice the results of experiments made in, and there- 

 fore applicable only to, particular cases. 



The results of experiments thus made at various times and places, 

 and without that identity of condition and circumstances so necessary 

 when standard rules are to to be detiuced from them, have, nevertheless, 

 been used for that purpose; and this circumstance, combined with the 

 various and disiinct points to be considered before we can estimate 

 accurately what even constitutes draught, will perhaps account for the 

 disagreement amongst the practical and scientific authorities alluded to on 

 the subject. 



We must, therefore, examine severally all these points ; and then, by 

 carefully considering their relative bearing upon rach other, we may hope 

 to reconcile the difierent opinions advanced, without which we cannot 

 collect from them any information which will ultimately lead us to a prac- 

 tical and beneficial result. 



We shall proceed to divide the subject under separate and distinct 

 heads, and under each head to examine the methods or means now in 

 use, or which have been proposed, and endeavour to estimate their com- 

 parative advantages by availing ourselves of what is already written and 

 known upon each. 



It will be necessary first, however, to explain and define clearly some 

 terms wliich will occur frequently in the course of this paper, and especially 

 the word "draught," wliich is the title itself of the treatise. 



This word is used in such a very general and vague sense, that it would 

 be difficult, if not impossible, to give an explanation which should apply 

 equally to all its different meanings. 



In the expression draught by animal power, it would seem to mean the 

 action itself of drawing, while, on the other hand, it is frequently used to 

 signify the amount of power employed; also, the degree of resistance, as> 

 when we say, the draught of a horse, or the draught of a carriage. Draught 

 power is also an expression used. We shall, however, in the course of 

 this treatise, confine our use of the word to the two meanings — draught. 

 the action of dragging — and draught, the resistance to the power employed 

 to drag any given weight. 



Force of traction is another expression requiring explanation ; but hert; 

 we must enter into more detail, and shall give at once a practical illustra- 

 tion of our meaning. 



A force is most conveniently measured by the weight which it would be 

 capable of raising ; but it is not therefore necessarily applied vertically, in 

 which direction weigh' or gravity acts. 



If a weight of 100 !bs. be suspended to a rope, it is clearly exerting upon 

 this rope a force of 100 lbs.; but if the rope be passed over a pulley void 

 of friction, and continued horizontally, or in any other direction, and then 

 attached to some fixed point, the weight still acts upon all parts of this 

 rope, and consequently upon the point to which it is fixed, with a force 

 equal to 100 lbs. ; and so inversely, if a horse be pulling at a rope A^.'th a 



