COMBUSTION. 157 



we spoke of the exceeding movability of water. As it courses 

 about much of it becomes resolved into its elementary gases, 

 oxygen and hydrogen, to engage in the formation of other 

 substances, gaseous, liquid, and solid; and just as constantly 

 new water is forming to take the place of that which is 

 thus resolved. Especially do such changes in water take 

 place when it enters living substances. The constituents 

 of water form a part of all vegetable and animal substances, 

 and it is, therefore, decomposed continually to furnish these 

 in the growth that is every where going on. 



QUESTIONS. 



167. Mention some of the various effects of combustion. 1G8. What was 

 Stahl's theory of phlogiston ? How long did his theory prevail ? 169. What 

 takes place in ordinaiy combustion? 170. Explain the experiment repre- 

 sented in Fig. 50. State what takes place in the burning of illuminating gas. 

 171. State the processes involved in the burning of a common candle. 

 How can you prove that water is formed in the burning of u candle ? How 

 that carbonic anhydride is formed ? 172. Describe the structure of a can- 

 dle's flame as mapped in Fig. 52, and the processes involved in the burning. 

 173. State the experiments shown in Figs. 53 and 54. Give the experi- 

 ment with the slip of wood. That with the match. State the experiment 

 represented in Fig. 55. 174. That represented in Fig. 56. State and ex- 

 plain the experiment with a slip of copper. 175. Illustrate the fact that in 

 the combustion of wood the formation of gas and its combustion are two 

 distinct processes. 176. What is the cause of flame ? 177. What is said of 

 the burning of anthracite ? What of the difference between anthracite and 

 bituminous coal? 178. What of the making of gas? 179. Mention cases 

 of combustion in which the results are aeriform ; cases in which they are 

 solid ; and cases in which they are partly solid and partly aeriform. What 

 proportion is there of solid when wood is burned? 180. How may combus- 

 tion be increased ? What is said of the chimneys and wicks of lamps ? 

 181. Describe the gas-lamp known as Bunsen's Burner. What are its ad- 

 vantages ? 182. Describe a blow-pipe. What is said about oxidizing and 

 reducing flames? How is a blow-pipe useful to chemists? 183. What is 

 said of improper management at fires ? 184. What of blowing out a can- 

 dle ? Explain the expedients resorted to for preventing lights from going 



