HORSE POWER, the power of an ordi nary horse or its equivalent, the force with which a horse acts when drawing. The mode of ascertaining a horse's power is to find what weight he can raise and to what height in a given time, the horse being supposed to pull horizontally. From a variety of experiments it is found that a horse, at an average, can raise 160 pounds weight at a volocity of two and a half miles per hour. The power of a horse exerted in this way is made the standard for estimating the power of a steam-engine or other motor. Thus we speak of an engine of 60 or 80 horse power, each horse power being estimated as equivalent to 33,000 pounds raised one foot high per minute, but this estimate is considered much too high, 17,400 foot-pounds per minute being generally considered nearer the truth. As it matters little, however, 'what standard be as sumed, provided it be uniformly used, that of Watt has been generally adopted. In esti mating horse power, it is important to re member the element of time; the shorter the time the greater the power exerted. The gen eral rule for estimating the power of an engine or motor in terms of this unit is to multiply to gether the pressure in pounds on a square inch of the piston, the area of the piston in inches, the length of the stroke in feet and the num ber of strokes per minute; the result divided by 33,000 will give the horse power 'deducting one tenth for friction. As a horse can exert its full force only for about six hours a day, one horse power of machinery may be said to equal that of four horses. The difference between an animal and a machine is further illustrated by the fact that any robust man can for a short time put forth more energy than this theoreti cal horse power; but he cannot maintain it, while the engine can, as long as it is in order and the power is applied. See ENGINEERING TERMS; INTERNAL COMBUSTION ENGINE, a national which has been called the sport of kings be cause it has been one of their amusements since the earliest dawn of civilization. The racing horse is of three distinct types, the running horse, the pacing horse and the trotting horse. For many centuries the running race has been the traditional turf sport in Great Britain and on the Continent, with many varieties, such as flat racing, or racing on level ground; steeple chasing, or racing over ground not specially prepared for the purpose, and hurdle-racing, in which the horses have to leap over obstacles purposely placed in the way. Trotting is pri
marily an American institution, the outcome of thoroughbred development. Late in the 19th century horse-racing made a wonderful ad vance in the United States and easily became the great national pastime of the country.
Early I, of the 18th Egyptian dynasty. left a papyrus letter telling of his conquest of Mesopotamia, and priding him self upon the acquisition of the racing horse (the Arab) and being the first to introduce him in Africa. Somewhat later the records tell of King Solomon buying horses from Egypt, and paying as much as $3,000 for some of them. Among the Greeks it was introduced into the Olympic games in the 33d Olympiad (648 ac.). From Greece it was introduced into Rome, where it gained a place as one of' the games of the circus. The institution of horse-races in England, where the sport has become a great national pastime, belongs to a very remote pe riod. The first regular horse-races, however, did not take place till the reign of James I. The successors of James I down to Queen Anne were all more or less attached to the sport. In the reign of the latter, in 1711, the York Plates were founded, and about that date the passion for betting on the turf began to be Under George I, the successor of ueen Anne, horse-racing became more flour ishing. The two most celebrated horses of that period were Flying Childers (foaled in 1715) and Eclipse (foaled in 1764), which long had the reputation of being the fleetest horses that ever ran. From the latter are descended many of the first-class thoroughbreds of the present day_ None of the English sovereigns was more devoted to horse-racing than George IV. Between 1784 and 1792, while yet Prince of Wales, he gained 185 prizes, including the Derby of 1788. Horse-racing was introduced into France from England during the reign of Louis XIV, and under Louis XV was pursued with the utmost enthusiasm.