XX 



GENERAL INTRODUCTION 



If you perform the experiment requiring the lime, be sure that you 

 start with a fresh piece of quick or stone lime, which can be had 

 of any lime or cement dealer. During the performance of the 

 following simple experiments, the pupil should describe what he 

 sees at each step. The questions inserted in the text are offered 

 merely as suggestions in the development of the desired ideas. 

 The answers are those which it is desired the pupils shall reach 

 or confirm by their own observation. 



I . Oxygen 



Light the candle and place it on a piece of blotting 

 paper (A). What do you see burning ? Is anything burn- 

 ing besides the candle ? The answer 

 will probably be " no." Let us see. 



Place the lamp chimney over the 

 lighted candle, and partly cover the 

 top by a piece of stiff paper, as in 

 Fig. A. Ask the pupils to observe 

 and describe how the flame goes out ; 

 i.e. that it is gradually extinguished 

 and does not go out instantly. Why 

 did the flame go out ? The probable 

 thought will be, 



A. — The Beginning of 

 the Candle Ex- 

 periment. 



" Because there was no air." (If there 

 was no air within the chimney, some 

 could have entered at the top.) 



Place two pencils beside the re- 

 lighted candle and on them the chim- 

 ney (B). What is the difference be- 

 tween the way in which the candle 

 burns now and before the chimney 

 was placed over it? It flickers, or 

 dances about more. What makes 



B. — Supplying Air un- 

 derneath the Chim- 

 ney. 



