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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 burning 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, "Because there was no air." (If there was no air within the chimney, some could have entered at the top.)

A.—

B.—

Place two pencils beside the relighted candle and on them the chimney (B). What is the difference between the way in which the candle burns now and before the chimney was placed over it? It flickers, or dances about more. What makes