General Thought Questions 169 



23. Is a hot air, a steam, or a hot water system better for ventilating a 

 building ? 



24. Why are furnaces and pipes often covered with asbestos or similar 

 materials? 



25. Why does a hot forest fire start a wind even on a windless day? 



26. What would be likely to happen if a cold tumbler were placed inside 

 one just heated in hot water? 



27. Why do we oil machinery? 



28. Why is it possible to tell the direction of a light wind by holding up 

 a moistened finger? 



29. Why does loosely woven clothing often keep us warmer than clothing 

 of close texture? 



30. Explain the lessening of a wind at sunset 



31. Name several changes that would be brought about if the earth 

 stopped rotating on its axis. 



32. Why does water whirl when draining out of a sink? 



33. Explain why flatirons often have handles of wood or coiled wire. 



34. How may you reduce the smoke caused by adding fuel to a fire? 



35. Why are telescope rooms in astronomical laboratories not heated? 



36. Why are fires especially troublesome when they start in partitions? 



37. How does the moon affect the earth? 



38. Why do steam pipes seem to snap and pound when heat is turned on? 



39. Why do water pipes pound when water is turned off sharply at the 

 faucet? 



40. Why do greenhouses have glass tops? 



41. Why does water kept in a porous jar stay cool in hot weather? 



42. Why do houses damaged by a tornado often appear to have been 

 blown apart from the inside? 



43. Could we use any other star than the North Star as a guide if lost 

 in the wilderness without a compass? 



44. Is it true or false that a barometer reads the same at a given hour 

 in all localities? 



45. Suppose there were placed before you a cup of mercury, a glass tube 

 34 inches long and a shallow dish, in order that you may use these 

 materials to perform a certain experiment. 



a. What experiment could you perform by using these materials? 



b. Describe just what you would do in the experiment. 



c. Show by a labeled drawing what would happen in this experiment 



d. What conclusion would you draw? 



