450 Introduction to the Study of Science 



cinder is removed from the iron. The cylindrical lump of iron 

 is called the bloom. 



The bloom is rolled into what is called the puddle bar. By the 

 rolling more of the cinder is eliminated, but the remainder is 

 drawn out into string-like shapes which force a lengthening of the 

 fibers of the iron grains enveloped in the cinder. The puddle bar 

 is cut into strips usually three and one half feet long, which 

 are piled together to equal the width of the bar or plate that is 

 to be the final product. The bundle of strips is tied together 

 with wire and placed in a furnace, where it is heated to a welding 

 temperature. The heated bundle is then rolled to a plate or bar 

 of the required dimensions. The usual length of the bars 

 produced is seventy feet. 



The finished bar is called in commerce the merchant bar. 

 Its structure as revealed by the aid of a microscope is interesting. 

 By the cutting, welding, and rolling the iron fibers have been 

 lengthened greatly and now form a closely compact bundle 

 of fibers, each of which is enveloped in its slag or cinder. The 

 additional rolling has removed a small amount of the slag from 

 the iron as it appeared in the puddle bar. But the final product 

 retains from three fourths to one and one half per cent of slag 

 or cinder. 



SUMMARY 



Iron is the most useful metal. It makes up 95 per cent of the total 

 tonnage of metals annually produced. The United States is the 

 greatest producer, with a yearly output of more than 60,000,000 

 tons. 



Iron is useful largely because of its strength, hardness, rigidity, 

 density, high melting temperature, and its capacity for mag- 

 netism. 



Iron in various compounds is distributed universally, as in the earth, 

 water, plants, and animals. In abundance it is fourth among the 

 elements. 



Many meteorites are composed almost entirely of iron. 



Iron ores include the iron oxids, as hematite, magnetite, and the 

 brown iron ores, iron carbonate and iron sulfid. 



