COMMON HAND-TOOLS 281 



and sand, which supplies the silicon. The coke is crushed 

 in a mill, and is then mixed with the sand. The mass of 

 raw material is then placed in an electric furnace for 36 

 hrs. and a current of 2000 electrical horse-power is passed 

 through it. 



The resistance thus interposed results in the generation of 

 enormous quantities of heat, so great is the temperature of 

 the resistance path; the surrounding mass of coke and sand 

 is heated to a point which is between 4000 and 4500 F. 

 In this terrific heat all known metals not only melt, but vola- 

 tilize (disappear in the form of a gas). Iron and steel are 

 turned to vapor and granite rocks melt away. All the im- 

 purities and substances in the coke and sand other than 

 carbon and silicon are destroyed or driven off in gaseous form, 

 and the atoms of these two elements fly together and unite 

 as carborundum. 



The total energy used in a single run of a carborundum 

 furnace is 72,000 horse-power hours. Incidentally, enough 

 electric power is consumed to operate an arc light continu- 

 ously night and day for twelve years, or to operate one 

 16 candle-power carbon incandescent lamp for two hundred 

 and twenty years. 



Questions 



1. Draw a sketch of a hammer removing a nail from a board. 

 Where is the fulcrum? 



2. Would you gain more advantage in holding the handle of 

 the hammer in the middle or the end? Explain. 



3. Why are hammers graded by weight? 



4. Why is the neck of the hammer made small? 



5. Name the common hammers and their uses. 



6. How does a chisel for cutting steel differ from one used in 

 cutting wood? Why? 



7. Explain the different forms of coJ4 chisels, 



