Photograph from Brown Brothers 



BUILDING FARM TRACTORS AT MINNEAPOLIS, MINNESOTA 



As population at home grows more dense and demands abroad multiply, steel as a labor 

 and food saver on the farm becomes of greater importance. When the farm tractor gen- 

 erally replaces the horse, it will release about 100,000,000 acres of farming land for other 

 purposes, as it requires the products of about five acres to maintain a work horse. This 

 totals nearly twice the area devoted to wheat growing in the United States in these dire 

 times when the whole world is begsrins" us for bread. 



with treatment it may be given almost 

 any degree of hardness after the heat has 

 left it. from the soft, weak iron casting to 

 the hard, strong tool steel. It may also 

 be given any color from silver white to 

 coal black. Cast iron is different from 

 steel in hardness and in color. It can 

 stand almost as much squeezing together 

 as the best steel, but it is comparatively 

 weak in resisting a pull apart. It can 

 stand a steady strain, but a sharp blow 

 will shatter it. In making cast iron the 

 cupola furnace is usually used, but not 

 always. A bed of coke is laid down, then 

 a layer of iron, then another layer of 

 coke, and so on. It is then tired, the iron 

 melts and runs out. and is poured into 

 molds. Air-brake parts, radiators, pipe 

 fittings, etc., are examples of the uses of 

 cast iron. 



The story of Bessemer steel is one of 

 the fascinating chronicles of the indus- 

 trial world. It seems to have been one 



of those cases where two men work- 

 ing in different countries, each without 

 knowledge of what the other was doing, 

 reached the same conclusion about the 

 same time. Both were granted American 

 patents : but upon application for re- 

 newal, the Patent Office held Kelly to be 

 the inventor. The world, however, gives 

 the credit to Bessemer, and the process 

 is known as the Bessemer process. 



Kelly was a maker of old-fashioned 

 cooking pots and kettles. It is related 

 that one day he was sitting in front of 

 his furnace and observed a point of in- 

 candescence where there was no char- 

 coal — only the metal and the air. This 

 led him to contend that air alone would 

 burn out the impurities from molten 

 iron. When he developed his tilting con- 

 verter, his engineer blew such a tremen- 

 dous blast through the first charge that 

 iron and all went up as sparks, to his 

 discomfiture and the crowd's amuse- 



150 



