5-28 OiN DRAUGHT. 



innrease the draught in the proportion of four to five ; while it was stated 

 l»y 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 dirain- 

 ished the draught in the proportion of five to four. 



Amidst such conflicting and contradictor}^ opinions it would appear 

 difficult to come to any usefal conclusion, and we might naturally be 

 disposed to adopt a reiy common practice, that of taking an average 

 i-esult. 



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

 pancies and contradictions arise in great measure from attempting to 

 generahse 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 

 A\dthout 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 variety of dis- 

 tinct points to be considered before we can estimate accurately what even 

 constitutes draught, will perhaps account for the disagreement among the 

 practical and scientific authorities alluded to. 



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

 «idering their relative bearing upon each other, we may hope to reconcile 

 the difi^'erent opinions advanced, wdthout 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 theii' comparative 

 advantages by availing ourselves of what is already written and knov^Ti 

 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 itself the title 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, as well as 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, confine 

 our use of the word to the two meanings — draught, the action of dragging 

 — and draught, the amount of resistance to the power employed to di'ag 

 any given weight. 



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

 here we must enter into more detail, and give a practical illustration of our 

 meaning. 



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

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

 ^^■hich direction weight or gravity acts. 



If a weight of 100 lbs. 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 puHy 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 with a 

 force which, if the rope were jiassed over a pully, would raise 100 lbs., 

 the force of traction of the horse is in this case 100 lbs. Spring steel- 



