THE ATMOSPHERE. 21 



23. What is the chemical name of the rust of iron ? 

 also of the dross of lead 1 



24. Why does covering the surface of metals, such as 

 iron or brass, with varnish or oil, prevent their corroding? 



25. Of what substance upon the surface of the earth, 

 except air, does oxigen constitute a part 1 



26. Which is most abundant in the vegetable kingdom, 

 oxigen or nitrogen 1 



27. Where is nitrogen most abundant, in animal or 

 vegetable matter ? 



28. If the atmosphere were pure oxigen, would it be 

 more or less favorable to respiration and combustion ? 



29. What appears to be the principal use of nitrogen 

 in the atmosphere 1 



30. How is the animal system affected by inhaling pure 

 oxigen ? 



31. How is animal life affected, if full inhalations of 

 carbonic acid be taken into the lungs ? 



32. Do the lungs throw off more or less oxigen than 

 they receive ? 



33. Do they throw off more or less carbonic acid than 

 they receive 1 



34. What other operations in nature, except respira- 

 tion, produce carbonic acid ? 



35. What substance which is fatal to life, is thrown off 

 by burning charcoal ? 



36. Is the carbonic acid in cider, beer, and soda water, 

 favorable, or unfavorable to health ? 



37. What natural agents are employed in evaporation 1 



38. What finally becomes of the moisture taken up and 

 carried off by the atmosphere ? 



39. What becomes of the water which falls into the 

 ocean, through the medium of rivers, rain, &c. 



40. Which is most compressible, air or water ? 



41. Does heat expand, or contract air 1 



42. What is the most powerful vehicle in nature, foi 

 transporting heat and moisture ? 



43. What is the cause of winds, and all motions of the 

 atmosphere ? 



44. In what part of the earth, and over how great a 

 space, does the wind blow in one direction through the 

 year ? 



