It is not enough to have good horses well nourished; their powers should be directed along most efficient lines. Figure 92 illustrates how one span may lift and roll out of its resting place a stone so large that it may require three spans of animals to draw it when placed on a stone-boat. However, oxen are better than horses for this purpose. If it is desired to haul a heavy log for a short distance, the chain is attached at the lowest point, or under the side of the log. In some of the old English works on plowing (Fig. 93), the line of draft is represented as starting at the center of resistance, thence running in a straight line through the clevice at the end of the beam, and ending where the traces are attached to the names. The American plowman uses short traces, which results in bending the line of draft upwards, thus diminishing the friction of the sole of the plow. (Fig. 94.) The bent line of draft tends, of course, to raise the plow out of the ground, but this is overcome by giving the point of the plow a little more pitch. It is often observed by farmers that tall horses appear to plow with less effort than low ones. This is no doubt a fact, since the line of draft is bent more by the tall horses than by the low ones. Horsemen all know that teams are most efficient in moving heavy loads when hitched close to them. The reasons for this may be found in the greater bend of the line of draft and in the greater traction power of the animals. In other words, the closer the horses are to their load, the more of the weight of the load is placed on the horse. His shoulders not being at right angles to the direction which the load is to take, a part of the load is thrown upon the body of the horse. This relieves some of the friction of the load and practically gives more weight to the horse, and this, in turn, tends to hold him to the ground and increases his traction power. In early days, farm products and merchandise were transported largely by teams of four or more horses. The smallest horse was put on the nigh (left-hand) side of the pole (tongue). The pole horses were not called on to do their full share of the work where the roads were good, but were kept in part as a reserve. When a supreme effort bad to be made, the driver leaped on to the little horse, when, for a short time, by reason of his added weight, he was nearly equal in draft power to the larger horse.
Fig. 92. Energy efficiently directed.
Fig. 93. Line of draft so low as to increase friction.
Fig. 94. High line of draft diminishes friction of sole of plow.
Low-wheeled wagons are becoming somewhat common on the farm; they should become more common, although they run harder, other things being equal, than wagons with wheels of standard size. However, the length of haul on the farm is so short that the increase of draft due to the small wheels may be ignored, especially since human physical energy is far more expensive than horse energy. It is not economical to lift heavy material unnecessarily high for the purpose of easing the horses, or for the fun of throwing the material down again. Farm-wagons should have, as a rule, wide tires, although, under some circumstances, they increase the draft over narrow-tired ones seriously. Wagons with wide tires run easier on hard pavements, be they smooth, as of brick or asphalt, or roughish, as when constructed of stone. But on dirt roads covered with two or three inches of stiff mud, the wide-tired wagon is a "horse-killer," or so pronounced to be by good teamsters. The use of wide-tired wagons tends to prolong the life of the good road; but this is no reason why wide-tired wagons should be used at the expense of horse-flesh to improve dirt roads which become "villainous" every spring and fall. Narrow tires push away and cut through the mud and find a hard bottom. Wide tires push down and climb over the mud, and by so doing the draft is increased.
When horses are used for draft purposes on pavements, their weight becomes a factor of prime importance. Manifestly, it is not convenient in great cities (especially American cities) to hitch several horses to one wagon. Fortunately, most of our streets are wide enough to permit of two being driven abreast, and, when so driven, they are most efficient in backing a load. On pavements, horses get but a precarious foothold for pulling. On moderately soft ground, they are able, by placing the feet well back, to bring the soles of the feet at an angle of fifteen to twenty degrees from the horizontal, or the direction of the movement of the load. On the smooth pavements, no such advantage can be taken, and here efficiency of draft depends largely on the weight of the horse. If, then, friction on the pavement becomes so important, can the line of draft be so adjusted as to increase it? It is evident that if the point of attachment to the load be low, the friction of the feet of the horse on the pavement will be increased; if the point of attachment be high, it will be diminished. Therefore the doubletrees should be placed in a supporting iron under the tongue of the wagon, especially if the wagon has low front wheels and is used for heavy traffic. The farther back the doubletrees are placed, and the shorter the traces, the more pronounced will be the angle of draft and the greater the traction power.
A horse weighing 1,500 pounds when tested, by placing the attachment to the load but six inches from the ground, was able to pull 2,310 pounds as measured by dynamometer. When he was attached to the load at the height of two feet, he was able to pull 1,980 pounds. When attached at a height of three feet, he was able to pull 1,732 pounds.
When horses are attached to light vehicles where light draft, rapid movement, safety and beauty are desired, the point of attachment to the vehicle should be high. Horses used for light work are often "frisky," and they may get over the traces if they are hitched low.
When driving a single horse to a light sleigh, he should be placed immediately in front of it, if he is to be driven only in the city. In the country, the horse is attached in front of the right-hand runner, that he may travel in the right-hand beaten track. In the United States, the law directs that, when teams meet, they shall turn to the right; in most European countries, teams meeting turn to the left, which is far safer and more convenient. The awkward American custom is due without doubt to the almost universal use of oxen in the pioneer days. Since oxen are driven by walking on the left side of them, it is most convenient to turn to the right. The driver of horses sits on the right; logically, he should turn to the left.
We now come to another method of attaching horses to two-wheeled vehicles, which first became common in London and later, happily, was introduced into some of our American cities. The hansom-cab is a light two-wheeled covered carriage with the driver's seat elevated behind, the reins being passed over the top. It is so balanced on the axle that, when loaded with one or two passengers and driver, the tendency is for the shafts (thills) to rise. This tendency is prevented by a wide, padded belly-band. This method of attachment practically transfers a part of the weight of the front end of the horse to the axle, and this results in great gain, as it relieves some of the concussion of the horse's front feet on the pavement. Since the draft of the load is light, the horse can well spare some of this weight, and this may result in preserving the soundness of the front feet. Many times, horses with front feet slightly affected are used in hansoms; because there is opportunity to relieve some of the pain due to slight unsoundness.
Fig. 95. Saves front feet of horse.