SCIENTIFIC READINGS. 117 



cury being 37 millions of miles distant, Venus 69 mil- 

 lions, the Earth 95 millions, Mars 144 millions, Jupiter 

 494 millions, Saturn 906 millions, and Georgium Sidus 

 1820 millions r 



COLD. 



140. What is Cold ? 



141. What effect has cold on bodies in general ? 



142. What is the highest degree of cold that has been 

 produced artificially ? 



143. What simple mixture will cause the thermometer 

 to sink suddenly from the freezing point to Zero ? 



144. In extreme cold, what is the consequence when 

 the external air is suddenly admitted into a sitting- 

 room ? 



145. What is the usual effect of extreme cold on the 

 system ? 



146. Under what circumstances, and when was it, that 

 70OO Swedes perished through extreme cold ? 



147- Relate the occurrence which took place at Terra 

 del Fuego, during a botanical excursion of Sir Joseph 

 Banks and others. 



PNEUMATICS. 



148. On what does the science of Pneumatics treat ? 



149. What are the component parts of the atmo- 

 sphere ? 



150. What figure does the atmosphere assume, through 

 the motion of the earth and the action of the sun ? 



151. Is there any gas in the atmosphere, independent 

 of its constituents, oxygen and azote ? 



152. What is the height of the atmosphere ? 



153. What is the whole weight of the atmosphere ? 



154. What is the greatest height that an aeronaut has 

 ascended ? 



155. How does air press ? 



156. What is, generally speaking, the greatest height 

 of the clouds ? 



157. At what rate does the density of the atmosphere 

 decrease ? 



