812 HORSESHOES 



Foot-pounds 



73 kilogrammetres per second = 642J 



or 4,500 kilogrammetres per minute = 32,549 

 or 270,000 kilogrammitres per hour = 1,952,948, 



being about one-seventieth part loss than the Britisli horse-power. 



This is also called an actual or real horse-power, to distinguish it from a nominal 

 horse-power. 



NOMINAL HORSE-POWBB is a conventional mode of describing the dimensions of a 

 steam-engine, for the convenience of makers and purchasers of engines, and bears 

 no fixed relation to indicated or to effective horse-power. The mode of computing 

 nominal horse-power, established amongst Civil manufacturers of steam-engines by the 

 practice of Boulton and Watt, is as follows : 



Assume the velocity of the piston to be 128 feet per minute x cube root of length 

 of stroke in feet. Assume the mean effective pressure to be seven pounds on the 

 square inch. 



Then compute the horse-power from these fictitious data, and the area of the 

 piston ; that is to say, 



Nominal H. P. = 7 x 128 x & stroke in feet 

 x area of piston in square inches -r 33,000 



= & stroke in feet x area of piston in inches 



47 nearly 



= & stroke in feet x diam. 2 in inches 

 60 



The indicated power of different engines usually exceeds the nominal power as 

 computed by the above rule in proportions ranging from \\ to 5. 



In the rule established by the Admiralty for computing nominal horse-power, the 

 real velocity of the piston is taken into account ; but the fictitious effective power of 

 seven pounds on the square inch is assumed consequently by the Admiralty rules. 



Nominal H. P. = velocity of piston in feet per minute 

 x area of piston in inches x 7 -1-33,000 



velocity in feet per min. x diam. 2 in inches 

 6,000 



The indicated power of marine engines ranges from once to three times, and is on 

 an average about twice the nominal power as computed by the Admiralty rule. 



Both the Civil rule and the Admiralty rule for computing the power of engines are 

 applicable to low-pressure engines alone. For high-pressure engines there is a 

 customary rule proposed by Mr. Bourne, which consists in assuming the effective 

 pressure to be 21 pounds per square inch, the other data being the same as in the 

 rule for low-pressure engines. See Kankine's ' Manual of the Steam Engine and other 

 Prime Movers.' 



HORSE-RADISH. The root of Cochlearia Armoracia, eaten as a condiment. 

 For the distinctions between the roots of horse-radish and monkshood, see ACOXITK. 



HORSESHOES. The ordinary method of making those is well known. There 

 has, however, been introduced with much success a machine for making horse- 

 shoos ; and one of these machines has been erected at Chillington Ironworks, Wolver- 

 hampton, by the inventor, Mr. Henry Burden, of Troy, New York. As early as 

 1835 he took out a patent for a machine for making horseshoes, which he improved 

 upon in 1843, and this was turned to practical account by the production of a con- 

 siderable number of horseshoes. The present machine, however, which was patented 

 in 1857, is entirely different from the former ones, and is a very remarkable piece of 

 mechanism. In the previous machines the piece of iron bar of which the shoo was to 

 be made was rolled into shape before being bent, and the pressure of the rollers being 

 in the direction of its length, the bar, when it was pressed, was naturally rather ex- 

 tended in length than width, and the widening which is required at the crown of the 

 shoo was not properly effected. By the present plan the bar, after being heated, 

 enters the machine by a feeding apparatus, a pioce of the required length is cut off, 

 iiri'l, by ;i stroke from a piece of steel, shaped liko the inside of a horseshoe, is bent, 

 and falls upon a die on a wheel beneath, corresponding to one on a cylinder abuvr, 

 and thus acquires by pressure the desired shape, two lateral strikers at th MOM 

 moment hitting the extremities,' or heels, of the shoe, and driving them inwards into 



