162 OUR PHYSICAL WORLD 



caught, and by proper treatment are turned into valuable com- 

 mercial products. Thus, wood alcohol, acetic acid, creosote, 

 tar, heavy oils, dyes, and many other valuable by-products are 

 saved. Indeed, it is said that the by-products are now so valu- 

 able that they pay the expense of operation, and the iron itself 

 is sold at a clear profit. In many furnaces the iron is no longer 

 run into "pigs" but is received as it runs from the stack in 

 caldrons on cars that take it to the puddling furnace or Bessemer 

 converters, where it is made at once into steel. 



The improvements in the process make it possible now to 

 produce more iron and steel in a single year than existed in the 

 whole world when Columbus discovered America. Then all the 

 iron existing would have made a pile 8X6 feet and less than a 

 mile long; now, a year's output is a pile of like size that would 

 reach from New York City beyond the Mississippi River ! Conse- 

 quently we use it lavishly, and its relative cheapness makes pos- 

 sible the immense quantity of labor-saving machinery now in use 

 in factories, on farms, and in homes. It has made possible our 

 great system of transportation, our railroads, locomotives, steel 

 freight cars, great steamships, automobiles, and trucks. This 

 is the age of steel. 



