OR, PLAIN TEACHING. 



137 



443. 



The name of one of the earliest steam loco- 

 motives was the Rocket, constructed by Messrs. 

 Booth & Stephenson. Its boiler was three feet 

 four inches in diameter, and six feet long' ; and 

 it exposed a heating surface of 1 17 square feet. 

 There were two cylinders, placed in a, diagonal 

 position, 5, with a stroke of 1G| inches, and 

 each worked a wheel, 9, 4 feet 8| inches dia- 

 meter, the connecting-rod being attached ex- 

 ternally to the spokes of the driving wheels. 

 The Rocket weighed 4| tons ; the tender, with 

 water and coke, 3 tons 4 cwt. ; and two loaded 

 carriages attached, 9£ tons ; so that the engine 

 and train together weighed about nineteen tons. 

 The boiler evaporated 1 14 gallons of water in 

 the hour, and consumed, in the same time, 217 

 pounds of coke. The average velocity of the 

 train was 14| miles an hour. 



The boiler of a locomotive con- 

 sists of a metallic cylinder, having 

 two flat ends, the cylinder being 

 common jjy about six feet in length. 

 The wider half of this cylinder, 

 10, is occupied by 

 about eighty or a 

 hundred copper 

 tubes, traversing 

 the whole length, 

 and each of about 

 1£ inches in diame- 

 ter. These tubes 

 are so many flues, 

 opening at both 



ends, the one end communicating 

 with the fire-box, or furnace, and 

 the other opening into the chim- 

 ney, thus affording a passage for 

 smoke and hot air. These pipes 

 being thus heated, they impart a 

 high degree of heat to the water 

 which surrounds them, the boiler 

 being filled with water to such 

 a height as to cover the tubes. 



The boiler, D, lies lengthwise 

 in the carriage, 442-3. The fire- 

 box, or furnace, f , is a square 

 box formed of two casings, the 

 one confained within the other. 

 The space within these two 

 casings is filled with water, and 

 forms part of the boiler. The 

 door, e, by which the fire is 

 supplied with coke, is made of 

 two iron plates, with a space of a 

 few inches between them. Thus 

 the fire is everywhere surrounded 

 either by water or confined air, 

 which prevents a great loss of 

 heat, in the rapid movement of 



