404 ON DRAUGHT. 



the draiig-ht 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 

 they 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 gene- 

 ralise and apply to practice the results of experiments made in, and 

 therefore applicable only to, particular cases. 



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

 and without that identity of condition and circumstance so necessary 

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

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

 various and distinct 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 

 considering their relative bearing upon each other, we may hope to recon- 

 cile the different opinions advanced, without which we cannot collect from 

 them any information which will lead us to a practical 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 which will occur frequently in the course of this paper, and especially 

 the word 'draught,' which 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 — draughty 

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

 to drag any given weight. 



Force of traction is another expression requiring explanation ; but here 

 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 weight or gravity acts. 



If a weight of lOOJbs. be suspended to a rope, it is clearly exerting upon 

 this rope a force of lOOlbs. ; but if the rope be passed over a pully 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 iOOlbs: and so inversely, if a horse be pulling at a rope with a 



