Now, Mr. Anderson has prepared some oxygen, and we will proceed to examine what is the character of this gas. First of all, you remember, I told you that it does not burn, but that it affects the burning of other bodies. I will just set fire to the point of this little bit of wood, and then plunge it into the jar of oxygen, and you will see what this gas does in increasing the brilliancy of the combustion. It does not burn--it does not take fire as the hydrogen would--but how vividly the combustion of the match goes on. Again, if I were to take this wax taper and light it, and turn it upside down in the air, it would in all probability put itself out, owing to the wax running down into the wick. [The Lecturer here turned the lighted taper upside down, when in a few seconds it went out.] Now, that will not happen in oxygen gas; you will see how differently it acts (fig. 26). [The taper was again lighted, turned upside down, and then introduced into a jar of oxygen.] Look at that! see how the very wax itself burns, and falls down in a dazzling stream of fire, so powerfully does the oxygen support combustion. Again, here is another experiment which will serve to illustrate the force, if I may so call it, of oxygen. I have here a circular flame of spirit of wine, and with it I am about to shew you the way in which iron burns, because it will serve very well as a comparison between the effect produced by air and oxygen. If I take this ring flame, I can shake by means of a sieve the fine particles of iron filings through it, and you will see the way in which they burn. [The Lecturer here shook through the flame some iron filings, which took fire and fell through with beautiful scintillations.] But if I now hold the flame over a jar of oxygen [the experiment was repeated over a jar of oxygen, when the combustion of the filings, as they fell into the oxygen, became almost insupportably brilliant], you see how wonderfully different the effect is in the jar; because there we have oxygen instead of common air. [Illustration: Fig. 26.] LECTURE IV. CHEMICAL AFFINITY--HEAT.