FASMERS' REGISTER— HORSE POWER AND STEAM. 



625 



game number of miles per day as the horse; but 

 from this gross amount of power we m.ust tle(Uict 

 that necessary to move the en<rine Avith ils supply 

 of coals: tliis will reduce it at least to 155 lbs., 

 consequenlly, in the one case we have a force ol 

 traction of 125 lbs., at an expense of 186 farth- 

 ings, and, in the other, a force of 155 lbs. at an 

 expense of 158 I'arthings; antl redncing them both 

 to one standard quantity oi" work done, we find 

 the expense of the horse is |^^.=1.488, and of 

 the loL-omutive engine 1.019, or about as 147 is to 

 100. In this case, therefore, there appears to be a 

 decided economy in the use of the steam-engine, 

 and accortlmgly its application has become very 

 general, and is becoming more so every day. 



Let us now' examine what alterations are requi- 

 site, before we can apply these calculations to the 

 case of draught upon common roads. Supposiag 

 both species of power equally convenient and ap- 

 plicaWe, and confining our observations merch' to 

 the amount of power and proportionate expense. 



The Ibrce of traction oi' the horse, and tlie 

 j-early cost, will remain so nearly the same, that 

 for oar present purpose we may consider them 

 quite unaltered. Not exactly so with the locomo- 

 tive engine. 



All the parts of the machine must be made much 

 stronger and heavier, and consequently more ex- 

 pensive for road work than for railway, and, there- 

 lore, the first cost Tv'ill be greater — the wear and 

 tear will also be greater, and as the work will be 

 more variable, the consumption of fuel will be 

 increased as well as the price; which, generally 

 speaking, will be much less on a line of railway, 

 than it can possibly be elsewhere. 



Still all these circumstances will not influence the 

 result so much as the increased effect of the 

 weight of the engine. On a railway with the car- 

 riage, as now constructed, the force of traction is 

 not much more than jl^r or ^^-^ of the weight 

 moved; consequently, the power necessary to move 

 the engine itself is not ver}- considerable. On a 

 road, hov.'ever, this proportion is materially alter- 

 ed; here the average force required to move a well- 

 constructed carriage cannot be estimated in prac- 

 tice, at less, even when the roads are in good re- 

 pair, than 77^; the engine, acconling to the con- 

 struction of the best locomotive engines now in 

 use, will weigh, with its carriages and fuel, at least 

 one-half ton, or 1120 lbs. per horse power, and ^V 

 of 1120 is nearl\' 45 lbs., which we have to deduct 

 from the gross power of the engine, and which 

 leaves onl}' 121f lbs. as the available power. The 

 proj)ortional expense of the horse and the steam- 

 engine is now therefore about as 115 to 100, and 

 this without taking into account the causes of in- 

 creased expenditure already alluded to as regards 

 the prime cost, the repairs, and the consumption of 

 fuel. From these calculations it would appear, 

 that; even if mechanical power was found as con- 

 venient and applicable in practice as horse power, 

 still no great economy can he expected from the 

 employment, upon common roads, of small loco- 

 motive engines, such as the best of those now in 

 use, and known to the public, unless it be in cases 

 where other means may tail to produce some par- 

 ticular effect which may be required; if, for instance, 

 a considerable velocity is necessary, the power of 

 a horse is very nearly exhausted in movinc; his 

 own body, and then th'^re can be no doubt that a 

 mechanical agent, in which power may always be 



exchanged for a proportional velocity, will have 

 some advantages on a very good road which 

 in fact approaches very nearly to a railway. But 

 in every case in which velocity is not a principal 

 object, as in the one now under consideration, and 

 wiiere, consequently, little momentum is acquired, 

 and frequent thought slight obstructions occur, as 

 on an ordinary road, an unimal ap|iears to possess 

 decided advantages. He adarsts himself admira- 

 bly to the v>^ork, increasing or diminishing liis ef- 

 forts according to the variations of the draught, 

 resting himself, as it Avere, and acquiring vigor 

 where his utmost strength is not called lor, and 

 thus becomes enabled to make exertions fiir be- 

 yond his average strength where any impediment 

 or obstruction is to be overcome. Indeed, he ap- 

 p>ears rather to increase the average effect of his 

 powers by these alternations of exertion and com- 

 parative relaxation; and wdten it is considered that 

 the draught will, in an ordinary road, frequently 

 vary in the proportion of six or eight to one, and 

 that these changes may succeed each other sud- 

 denly, the importance of such an accommodating 

 faculty v/ill be immediately appreciated. 



By mechanical povver, such as a .«team-engine 

 affords, these advantages are not easily obtained. 

 Without great weight or rapid motion no ra^omen- 

 tum can be acquired; and the carriage itself, not 

 being in rapid motion, and the necessary economy 

 in weight precluding the use of a flj^-wheel, any 

 snmll obstruction will check, and perhaps totally 

 stop the machine. For instance, supposing the 

 carriage to be advancing steadily under the effect 

 of a force of traction of 500 lbs., and that a stone 

 or rut suddenly causes aresistance, which it would 

 require GOO or 800 lbs. to overcome, a case by no 

 means rare even on tolerable roads; if the impetus 

 or momentum of the mass be not sufficient to car- 

 ry it over this obstruction, the machme nuist stop 

 until some increased power be given to it. 



It is also to be remembered, that what we are 

 accustomed, in practice, to consider as the avcrarre 

 ])o^ver of a horse, is the average excess remain- 

 ing over and above that necessary to carry hif3 

 own body; and that in all ordinary cases he is 

 able to maintain and continue nearly the same 

 exertions, although the comparative draught of 

 the carriage be considerably increased. Thus, 

 if the road be slightly muddy or sandy, or newly 

 gravelled, the draught, as v,-e shall see more accu- 

 rately laid down when we come to the subject of 

 wheeled carriaijes, will be double and even treble 

 what it is on the same road when freed from dust 

 or dirt; but the average power of the horse re- 

 mains nearly the same, and, practically speaking, 

 equal under both circumstances; that is to say, 

 that the power necessaiy to move the weight of the 

 horse's body, which forms no inconsiderable por- 

 tion of his whole power, is not materially increas- 

 ed by a state of road which will even treble the 

 draught of the carri;ige; consequently, the excess, 

 or available portion of his power, remains unim- 

 paired, and the full benefit of it, as well as ot^ any 

 increased exertions of the animal, is ['e\i and is ap- 

 plied solely to draggitig the load. 



Not so with a locomotive steam-engine, because 

 beyond the power necessirvto per.'brm tlie woj'k of 

 dracTfrincr the load, an additional power must be 

 provided to move the enirine itself. In other words, 

 if an enu'ine of ten-horse powvr be capable of 

 dragging a certain load, the weight of this engine 



