QUESTIONS. 329 



is illuminating gas obtained from bituminous coal ? What is coke ? 

 How is it supposed that anthracite coal was produced? How is it 

 like coke ? How does it differ from it ? What is its ordinary com- 

 position ? From what does redness in the ash come ? What is said 

 of slag ? Why do oyster-shells thrown into a coal fire remove the 

 slag or clinker ? What is said of certain uses to which anthracite is 

 sometimes applied ? 



28. What is said of the varieties of bituminous coal ? What of the 

 mineral called jet ? What is lignite ? What proofs are there that 

 coal is of vegetable origin ? 



29. How does carbon as it is in wood differ from carbon as it is in 

 coal ? Give the comparison in relation to its combination in wood. 

 Give in full what is stated in regard to the change in producing coal. 

 What is peat, and how is it made ? 



30. What is said of the depth and extent of peat beds ? What of 

 the diffusion of coal in the earth? What is amber? What are its 

 properties ? What its uses ? What is said of specimens of it and 

 imitations of them ? 



31. How are the different kinds of bitumen produced? What is 

 said of asphaltum ? What of petroleum ? 



32. What of naphtha ? What is the composition of carbonic acid 

 gr-s ? What are its qualities ? From what sources is it supplied to 

 the atmosphere? How is its undue accumulation in the atmosphere 

 prevented ? What is said of localities where it is produced in large 

 amount ? State in full what is said of its agency in relation to lime- 

 stone. What is said of the natural production of illuminating gas in 

 some localities ? 



CHAPTER IV. 



33. What is said of the crystallization of sulphur? What of its lo- 

 calities? From what ores is much of our sulphur obtained? What 

 are some of its uses ? 



34. What is the common iron pyrites, and why is it so called? 

 What are the forms of its crystals ? What mistake is often made 

 about it? How is it distinguished from gold? What use is made of 

 it ? What are the two other kinds of iron pyrites mentioned ? What 

 is said of copper pyrites ? What is copper glance? What is said of 

 a snlphuret of a very compound character? 



35. What is galena ? What is said of it ? In what parts of the 

 United States is it found abundantly ? What is said of the sulphuret 

 of silver ? What of the sulphuret of antimony ? What of the sulphu- 

 rets of arsenic ? 



36. What of the sulphuret of mercury? What of the su-lphuret of 



