G28 



FARMERS' REGISTER— LABOR OF HORSES. 



boats; the lengtli and curve of the rope f^ive an 

 elasticity to tjio strain, and the nccpssitv of keep- 

 ing tlie rope out of tiie water, or li-om dragnfing 

 along the towing-path, compels the animal to l<eep 

 up a constant, unremitted pull, and that, too, in an 

 obUque direciion, so as to throw him into an un- 

 favorable position. We accordingly find that, un- 

 der these circumstatices, the average work of a 

 horse is equivalent only to about four-fifths of that 

 given by Smeatgn, Desaguiiliers, and others, who 

 estimated the power of the horse from the work 

 done in a horse-mill, where the resistance is inelas- 

 tic, and all circumstances favorable, whh the ex- 

 ce|)tion of the circular path. 



The disadvantage of this kind of resistance is 

 well known, to carmen, though of course without 

 consideration of the reason. A horse is said to 

 pull better when he is close to his work, that is to 

 say, when he is attached at once to the body to be 

 moved, because everj^ exertion he makes is then 

 communicated at once to the mass; but the leader 

 of a team, unless he keeps the traces constantly on 

 the stretch, may frequently waste a powerful effort 

 without producing much effect upon the car- 

 riage. 



Another inconvenience resulting from harness- 

 ing horses in a team, or one before the other, is, 

 that the leader, by tightening the traces, is con- 

 tinually relieving the strain from the body horse, 

 and reciprocally the body horse from the leader: 

 so that these horses labor under all the disadvan- 

 tages of a long, elastic, and constantly yielding 

 connexion with' the load, which is not only fa"- 

 tiguing to them, but, in cases where the resistance 

 is variable, prevents the full and united effect of 

 their exertions being properly comm.unicated to 

 the carriage. For, if a slight obstacle, as a rut or 

 stone in a road, checks the progress of the vehicle, 

 the shaft-horse can immediately throw his whole 

 weight into the collar, and the united effect of his 

 strength and impetus is conveyed unimpaired to 

 the vehicle, and forces it over the obstacle; but if 

 any elasticity is interposed between the power 

 and the resistance, as in the case of the traces of 

 the leader of' a team, the whole, or the greater 

 part of the effect of impetus is lost, and that force, 

 which, if concentrated in one efibrt, would effect 

 the object, being lengthened into a continued and 

 comparatively feeble" pull, is insufficient. 



If we wish to destroy the impetus of a body 

 moving v»^ith violence, we receive it with a yield- 

 ing resistance; the action of catching a cricket- 

 ball exemplifies this perfectly; and therefore, if the 

 full effect of momentum is wanted, all elasticity in 

 the direction of the movement should be avoid- 

 ed. 



We have entered rather fully into the considera- 

 tion of this particular point, because the principle 

 is not only applicable to the mode of communi- 

 cating the iinmediate action of the movino: power, 

 but will be fovmd also of considerable importance 

 when w& arrive at the subject of wheel-car- 

 riafjes. 



A consideration of these various points brings 

 us to this conclusion, that the draught ought nei- 

 ther to be constantly uniform or without remission, 

 nor yet yieklingor elastic: sadden shocks or violent 

 changes in the velocity must also evidently be dis- 

 advantageous, as tending to distress and iriju-e the 

 animal. 



Having determined upon the necessary quality 



of the resistance, Ave will proceed to examine into 

 the quantity or the degree of resistance or draught, 

 and the speed best adapted to the exertion of the 

 animal. The useful efi(?ct of a horse, or the work 

 done, must evidently depend upon three things, 

 viz. the rate at which he is made to travel, the 

 power of traction he can exert, and the number of 

 hours he can continue to ivork daily at that speed; 

 and wliere there is no fixed condition which deter- 

 mines any one of tliese, such as a particular load 

 to be moved, or a certain velocity wliich it is desi- 

 rable to attain, or a limited time to perform the 

 work in, then the object must be to search for 

 those proportions of the three by which, at the end 

 of the day, the greatest quantity of work shall 

 have been produced. 



With respect to the first tivo, viz., Ilie speed and 

 power exerted, it will be obvious, that where a 

 horse travels unloaded, the greatest distance he 

 can go in any given time lor several daj's in suc- 

 cession without injurious fatigue, is the'Umit of his 

 velocity: on the other hand, the load may be so 

 great, that he can scarcely put it in motion — this is 

 the limit of his power: in both cases, the uselitl 

 effect is nothing. But between these hmits of ve- 

 locity and power, there is a proportion which af- 

 fords the maximum quantity of effect, and which, 

 therefore, must be the most advantageous for the 

 application of horse-power. 



It has been asserted by theorists, and the theory 

 appears to be supported by experience, that the 

 velocity corresponding to this nsaximum, or thatat 

 which a horse working continually a certain num- 

 ber of hours per day will do the most v/ork, is 

 equal to half the extreme or limit of velocity of 

 the same horse working the same number of liours 

 unloaded; and that the force of traction cori-es- 

 ponding to this speed, is equal to Ijalf the limit of 

 his power. For instance, if six hours be the 

 length of a day's work decided upon, and if a 

 horse working that time can go six miles per hour 

 unloaded, and therefore producing no useful efi'ect, 

 and supposing the limit of power of the same 

 horse be equal to 250 lbs., it is found that he will 

 do the most work in the same number of hours 

 when drawing a load at the rate of half six, or 

 three miles per hour; and half of 2.50 or 125 lbs. 

 will be the strain corresponding to this speed. Our 

 next step, then, must be to find these limits: now, 

 the limit of \"elochy depends upon the length of 

 time during which the speed is kept up; we subjoin 

 therefore a table deduced from experiments, and 

 which represents the proportion of the duration of 

 labor and maximum velocity of the average of 

 horses accustomed to their respective velocities. 



Hours. 



Duration > 12 3 4 5 



ot labor *) 

 Maximum ve- ^ 



Incityunloa- j^- j^^ iqi 31 7^ G^ G 5% 

 (led m miles -^ ^ ^ j ^ 



per hour J 



This Avithin the range here given maj' 

 dered as very nearly the law of decrease of speed 

 by increased duration of labor; and at the first 

 glance we see the great ;idvantage of reducing the 

 speed and prolonging the exertion. There are, 

 however, many causes to limit the duration of a 

 day's work of a horse. Tredgold, in his work on 

 railways, before quoted, says: 'the time assigned 



8 10 



41 



be consi- 



