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SCIENCE OF HOME AND COMMUNITY 



network over the whole country. The older forms of travel, 

 by horseback and stagecoach, have gradually become of 

 less importance, and the railroad has now become the chief 

 means of long distance travel. 



Having learned something about the important part 

 that the locomotive plays in everyday life and something 

 of its history, let us now study a modern locomotive to see 

 how it is built and how it works. 



Parts of a locomotive. The locomotive consists of three 

 essential parts : first, the fire box and boiler, that generate 

 power ; second, the cylinders and their valve gear, that use 

 the power; and third, the wheels on which the locomotive 

 moves. 



FIG. 91. First locomotive in United States. 



Boiler and fire box. The purpose of the fire box and boiler 

 is to convert large amounts of water into steam in a short 

 time. In order to do this, there must be a large amount of 

 heating surface, with heat on one side and water on the other, 

 so that large quantities of water will be in contact with the 

 heated surfaces. There is a direct heating surface on the 

 boiler immediately over the fire box, and in addition to this 

 there is the indirect heating surface made by using small 

 tubes about two inches in diameter, to carry off the heated 

 gases from the fire box to the smokestack. About 200 of 

 these tubes run through the boiler and are surrounded with 

 water. By means of these tubes a heating surface of 2500 

 square feet may be obtained, that is, equal to an area 50 feet 

 square. 



