QUESTIONS ON THE 



158. What effect is produced on the system at the 

 tops of mountains, through the extreme rarity of the 

 air? 



159. At what rate, on every square inch of surface, 

 does the air press ? 



160. Why will not the quicksilver rise higher than 

 about 31 inches in the barometer ? 



161. Within what height from the earth do the sun's 

 rays, in passing through the atmosphere, begin to suffer 

 refraction ? 



162. Describe an easy experiment, showing the up- 

 ward pressure of the air ? 



163. What quantity of oxygen, or the pure part of 

 air, does a man consume in an hour ? 



164. W 7 hy is it unwholesome to remain shut up in a 

 newly plastered or whitewashed room ? 



165. Where is it that the air is so affected by exha- 

 lations of a coppery nature, as to tarnish the silver in 

 the pocket ? 



166. What is the effect of heat on air ? 



167. What is the cause of Wind ? 



1 68. Describe an experiment, calculated to show the 

 effect of heat in rarefying the air. 



169. On what principle are fire-balloons made ? 



170. What would be the result if the air had no re- 

 flective power ? 



171. What is the cause of twilight? 



172. Describe Montgolfier's balloon. 



173. What are the principal instruments used to show 

 the various phenomena of the atmosphere ? 



174. Why will water boil sooner on the top of a high 

 mountain than in a valley ? 



175. Where will water boil soonest, or with a less 

 degree of heat, and why at the bottom of a deep mine, 

 or on the earth's surface ? 



176. What is the use of the Air-pump ; and by whom 

 was it invented, and when ? 



177- When a vessel has been partially exhausted by 

 means of the Air-pump, through what principle is it that 

 the remaining air fills the whole of the vessel ? 



178. On what does the weight of bodies depend ? 



