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It consists in an endless chain, a-a-a, made of planks, about an inch and a half thick, and four inches wide, extending across the bed of the carriage, attached at their extremities to ropes, and carried over a drum b-b at each end of the carriage, as shown in the plan at Fig. 2. To strengthen these cross pieces, and to prevent one of them from slipping down by itself, a cleat c-c is nailed on the end of each, and extends half-way across those next to it, on each side: the position of these, as they pass over the drums hi in, will best show their extent and attachments.
The chain platform is supported on a series of anti-friction rollers e-e-e-e. The horse is yoked to the frame, and, by treading on the movable platform, drives it round, by which the drums b-b are made to revolve, and, through the medium of the spur wheels, shown in the plan, puts in motion the carriage wheels.
Two sets of spur-gear are provided, one at each end of the drum, so that either may be put in action at pleasure, and be adjusted according to the nature of the road, whether ascents, descents, or on horizontal planes, the speed or power being duly proportioned to the plane operated upon; r-a represents the rope which is attached to the endless chain, and w-w the railway.
It will be observed, that by this arrangement the horse employed to propel the carriage is carried along with it, and thus a velocity of motion is produced in the machine far beyond the limits at which a horse can exert his power. Now, as it has been ascertained that the resistance from friction on a level railway does not increase with an increase of speed, it follows, that in many cases much advantage might be obtained, by an increase of velocity greatly exceeding that at which a horse could exert his power, or even travel on the road, without exerting any power of traction. The principal objection raised against this plan is, that the horse has to carry his own weight; but this objection equally applies to the locomotive steam-engine, in which the weight of one-horse power, including the water and fuel, falls very little, if at all, short of the weight of a draft horse. If we, however, suppose that the weight is increased thereby half a ton for the horse, it only amounts to a thirtieth part of his power of traction.
An ordinary horse exerts throughout the day a force of 150 lbs. when moving at the rate of two miles an hour, and this is equivalent to 36,000 lbs. moved upon the Manchester and Liverpool railway,. It has been shown upon several railways that horses can, and do, move the load we have mentioned at their ordinary working pace. But it is to be presumed that such an arrangement of mechanism may be (though it has not yet been) produced, as will enable a horse, duly trained, to apply a portion of his weight as a mechanical force, in addition to his muscular exertion, which would render this mode of employing animal power highly effective and useful. There have been many attempts, prior to Mr. Brandreth's, to apply horse power on the same principle; and it may be considered that they have hitherto all failed, from their not being continued in use: we are, nevertheless, of opinion, that the subject is still worthy of the attention of the mechanic.
To discover the cause of the great increase of speed, and the variable quantities of fuel consumed by the different locomotive engines, which competed for the prize at the Manchester and Liverpool railway, Mr. Wood instituted the comparative view of each, which is exhibited in the following table, and to which we shall append his judicious comments.