Page:EB1911 - Volume 13.djvu/745

 in the accounts of the adventures of the buccaneers, is still in frequent use among the sailors of all nations. Some ninety different kinds are known—the majority being wholesome food, and some of the species attaining a length of 3 ft. and more. The fish to which the name horse-mackerel is applied in Great Britain is Caranx trachurus, distinguished by having the lateral line in its whole length armed with large but narrow bony plates. Horse-mackerel are found singly on the coast all the year round, but sometimes they congregate in shoals of many thousands. Although well-flavoured, they are much more frequently used for bait than for food. This species has a most extraordinary range, being found almost everywhere within the temperate and tropical zones of the northern and southern hemispheres.  HORSEMANSHIP, the art of managing the horse from his back and controlling his paces and the direction and speed of his movement. The ordinary procedure is dealt with in the articles on and cognate subjects (see also : section Management). A special kind of skill is, however, needed in breaking, training, bitting and schooling horses for a game like polo, or for the evolutions of what is known as the haute école. It is with the latter, or “school” riding, that we deal here. The middle ages had seen chivalry developed into a social distinction, and horsemanship into a form of knightly prowess. The Renaissance introduced the cultivation of horsemanship as an art, with regular conditions and rules, instead of merely its skilful practice for utility and exercise. In Italy in the 16th century schools of horsemanship were established at Naples, Rome and other chief cities; thither flocked the nobility of France, Spain and Germany; and Henry VIII. of England and other monarchs of his time had Italians for their masters of the horse. The academy of Pignatelli at Naples was the most famous of the schools in the middle of the 16th century, but a score of other less renowned masters devoted themselves to teaching the riders and training the horses. Trappings of all sorts multiplied; the prescribed tricks, feats and postures involved considerable dexterity; they were fatiguing to both man and beast, and were really useless except for show. This elaborate art, enthusiastically followed among the Romance nations, was the parent of later developments of the haute école, and of the circus-performances of modern days. In England, however, the continental style did not find favour for long. The duke of Newcastle’s Méthode nouvelle de dresser les chevaux (1648) was the leading text-book of the day, and in 1761 the earl of Pembroke published his Manual of Cavalry Horsemanship. In France a simplification was introduced in the early part of the 18th century by La Guérinière (École de cavalerie) and others. The French military school thus became the model for Europe, though the English style remained in opposition, forming a sort of compromise with the ordinary method of riding across country. In more modern times France again came to the front in regard to the haute école, through the innovations of the vicomte d’Aure (1798–1863) and François Baucher (1796–1873). Baucher was a circus-rider who became the greatest master of his art, and who had an elaborate theory of the principles involved in training a horse. His system was carried on, with modifications, by masters and theorists like Captain Raabe, M. Barroil and M. Fillis. In more recent times the style of the haute école has also been cultivated by various masters in the United States, such as H. L. de Bussigny at Boston.

See d’Aure, Traité d’équitation (1847); Hundersdorf, Équitation allemande (Bruxelles, 1843); Baucher, Passe-temps équestres (1840), Méthode d’équitation (1867); Raabe, Méthode de haute école d’équitation (1863); Barroil, Art équestre; Fillis, Principes de dressage; Hayes, Riding on the flat, &c. (1882).

 HORSENS, a market town of Denmark, at the head of Horsens Fjord, on the east side of Jutland, 32 m. by rail S.W. of Aarhus, in the amt (county) of that name. Pop. (1901) 22,243. It is the junction of branch railways to Bryrup and to Törring inland, and to Juelsminde on the coast. The exports are chiefly bacon and butter; the imports, iron, yarn, coal and timber. The town is ancient; there is a disused convent church with tombs of the 17th century, and the Vor-Frelsers-Kirke has a carved pulpit of the same period. Horsens is the birthplace of the navigator Vitus Bering or Behring (1680), the Arctic explorer. To the north lies the picturesque lake district between Skanderborg and Silkeborg (see ).  HORSE-POWER. The device, frequently seen in farmyards, by which the power of a horse is utilized to drive threshing or other machinery, is sometimes described as a “horse-power,” but this term usually denotes the unit in which the performance of steam and other engines is expressed, and which is defined as the rate at which work is done when 33,000 ℔ are raised one foot in one minute. This value was adopted by James Watt as the result of experiments with strong dray-horses, but, as he was aware, it is in excess of what can be done by an average horse over a full day’s work. It is equal to 746 watts. On the metric system it is reckoned as 4500 kilogram-metres a minute, and the French cheval-vapeur is thus equal to 32,549 foot-pounds a minute, or 0.9863 of an English horse-power, or 736 watts. The “nominal horse-power” by which engines are sometimes rated is an arbitrary and obsolescent term of indefinite significance. An ordinary formula for obtaining it is D2 ∛ S for high-pressure engines, and D2 ∛ S for condensing engines, where D is the diameter of the piston in inches and S the length of the stroke in feet, though varying numbers are used for the divisor. The “indicated horse-power” of a reciprocating engine is given by ASPN/33,000, where A is the area of the piston in square inches, S the length of the stroke in feet, P the mean pressure on the piston in ℔ per sq. in., and N the number of effective strokes per minute, namely, one for each revolution of the crank shaft if the engine is single-acting, but twice as many if it is double-acting. The mean pressure P is ascertained from the diagram or “card” given by an indicator (see ). In turbine engines this method is inapplicable. A statement of indicated horse-power supplies a measure of the force acting in the cylinder of an engine, but the power available for doing external work off the crank-shaft is less than this by the amount absorbed in driving the engine itself. The useful residue, known as the “actual,” “effective” or “brake” horse-power, can be directly measured by a (q.v.); it amounts to about 80% of the indicated horse-power for good condensing engines and about 85% for non-condensing engines, or perhaps a little more when the engines are of the largest sizes. When turbines, as often happens in land practice, are directly coupled to electrical generators, their horse-power can be deduced from the electrical output. When they are used for the propulsion of ships recourse is had to “torsion meters” which measure the amount of twist undergone by the propeller shafts while transmitting power. Two points are selected on the surface of the shaft at different positions along it, and the relative displacement which occurs between them round the shaft when power is being transmitted is determined either by electrical means, as in the Denny-Johnson torsion-meter, or optically, as in the Hopkinson-Thring and Bevis-Gibson instruments. The twist or surface-shear being proportional to the torque, the horse-power can be calculated if the modulus of rigidity of the steel employed is known or if the amount of twist corresponding to a given power has previously been ascertained by direct experiment on the shaft before it has been put in place.  HORSE-RACING. Probably the earliest instance of the use of horses in racing recorded in literature occurs in Il. xxiii. 212-650, where the various incidents of the chariot-race at the funeral games held in honour of Patroclus are detailed with much vividness. According to the ancient authorities the four-horse chariot-race was introduced into the Olympic games as early as the 23rd Olympiad; to this the race with mounted horses was added in the 33rd; while other variations (such as two-horse chariot-races, mule races, loose-horse races, special races for under-aged horses) were admitted at a still later period. Of the training and management of the Olympic race-horse we are left in ignorance; but it is known that the equestrian candidates were required to enter their names and send their horses to Elis at least thirty days before the celebration of the games commenced, and that the charioteers and riders, whether owners or proxies, went through a prescribed course of exercise