FIRE AND ITS USES 



159 



Possibly the process was discovered when some savage used an 

 easily reduced ore of iron like siderite (see p. 50) to build a fire- 

 place, and found after many fires a bit of iron in it that could be 

 hammered out into serviceable shape. At any rate, the iron 

 forge among some African and Asiatic tribes is today simply a 

 hole dug in a high clay bank to serve as a fireplace in which a 

 charcoal fire is built and bits of iron ore and limestone are added, 

 then more charcoal, limestone, and iron ore, layer after layer. 

 The wind may furnish the draft, or simple bellows made of the 



FIG. 63. The weather map one day later than Figure 62 



skin of an animal may be used. After the fire has been kept 

 going for many hours it is allowed to go out, and at the bottom 

 of the hole there is dug out of the ash and debris a bit of iron. 

 Such a process of reduction is exceedingly slow. The quantity 

 of iron produced is small and it, therefore, is very costly. Iron 

 was, among early peoples, often used as money. 



The modern furnace does not differ in principle of operation 

 from such a primitive affair as that described. The ores of iron 

 most commonly used are oxides of iron, chemical unions of iron 

 and oxygen. They melt at high temperatures at which the 



