ON DRAUGHT. friy 



yards being now commonly in use, ^ye may be permitted to refer to tbem 

 as affording anotber clear exemplification of our meaning. In pulling at 

 a steel-yard of tbis description, if tbe same force be exerted, wbetber 

 borizontally or vertically, tbe index will, of course, sbow tbe same amount; 

 and, consequently, if tbe strengtb of tbe liorse be measured by attacbiug 

 tbe traces to one of tbese steel-yards, tbe number of pounds indicated on 

 tbe dial will be tbe exact measui'e of tbe strain tbe borse exerts, and tbe 

 amount of strain is called bis ' force of traction.' 



Having fixed as neai'ly as possible tbe meaning of tbese terms, wbicb 

 ■will frequently occur in tbe course of our progress, we sball proceed to tbe 

 division of tbe subject. 



It is evident tbat tbere are tbree distinct agents and points of considera- 

 tion in tbe operation of draugbt, wbicb are quite independent of each 

 otber. Tbey are — First, tbe moving power and tbe mode of applying it ; 

 Secondly, tbe vebicle for conveying tbe weigbt to be moved ; Tbirdly, tbe 

 canal, road, or railway, or Avbat may be generally termed tbe cbannel of 

 conveyance. 



All tbese individually influence tbe amount of draugbt, and require 

 separate consideration ; but tbe mode of combining tbese different agents 

 bas also a material effect upon tbe result, — consequently, tbey must be 

 considered in relation to eacb otber ; and to obtain tbe maximum useful 

 effect, witb tbe greatest economy, in tbe employment of any given power, 

 it is e\'idently necessary tbat tbese different agents sbould not only eacb 

 be tbe best adapted to its purpose, and perfect to tbe greatest possible 

 degree, but also tbat tbey sbould all be combined to tbe greatest advantage. 



We sball proceed, tben, to examine tbe different agents now employed, 

 tbe modes of applying tbem, and tbe proportionate effects produced. 



And, first, witb regard to tbe species of moving power ; — tbis may be of 

 two kinds, animal and mecbanical. 



By 'animal power' we mean tbe direct application of tbe strengtb of 

 any animal to dragging or pulling, as in tbe simple case of a borse 

 dragging a cart. By ' mecbanical,' tbe apjDlication of any power tbrougb 

 tbe intervention of macbinery : tbe source of power in tbis latter case may 

 stUl, however, be animal power, or a purely mecbanical agent, as a steam- 

 engine. 



The latter is the only species of mecbanical power which it has been 

 attempted, witb any prospect of success, to apply practically to loco- 

 motion ; and therefore tbat alone we propose to compare witb the animal 

 power. 



Now, although these two powers, viz., simple animal power and the 

 steam-engine, may in most instances be apphed so as to produce tbe same 

 effect, and may therefore, to a superficial observer, appear similar ; yet 

 tbere do exist such essential differences in the mode of action, or tbe means 

 by wbicb tbe effect is produced, tbat tbere are many cases in which tbe one 

 may be used, wherein tbe otber may be totally inapplicable. 



In tbis treatise, draugbt by anmial power is tbe principal object of con- 

 sideration ; but as great efforts have been made for many years, and are 

 still now perseveringly made, to supersede animal power entirely by me- 

 chanical, — to dismiss our old servant tbe horse, and supply his place by 

 the steam-engine, — it may be as well, in justice to tbe former, to say a 

 few words in bis defence, and to take a brief view of tbe distino-uisbing; 

 features of tbe two agents. 



To enter into all tbeii" respective merits, and to weigh their comparative 

 advantages in all circumstances, would involve us in many questions foreign 

 to tbat under our immediate consideration, and would embrace subjects 

 wbicb may supjily matter well worthy of our future attention. It is sufficient. 



M M 



