with by us--that none of these strange and injurious actions take place
when we are burning, not merely a candle, but gas in our streets, or fuel
in our fireplaces, so long as we confine ourselves within the laws that
Nature has made for our guidance.




LECTURE V.

OXYGEN PRESENT IN THE AIR--NATURE OF THE ATMOSPHERE--ITS PROPERTIES--OTHER
PRODUCTS FROM THE CANDLE--CARBONIC ACID--ITS PROPERTIES.


We have now seen that we can produce hydrogen and oxygen from the water
that we obtained from the candle. Hydrogen, you know, comes from the
candle, and oxygen, you believe, comes from the air. But then you have a
right to ask me, "How is it that the air and the oxygen do not equally
well burn the candle?" If you remember what happened when I put a jar of
oxygen over a piece of candle, you recollect there was a very different
kind of combustion to that which took place in the air. Now, why is this?
It is a very important question, and one I shall endeavour to make you
understand: it relates most intimately to the nature of the atmosphere,
and is most important to us.

We have several tests for oxygen besides the mere burning of bodies. You
have seen a candle burnt in oxygen, or in the air; you have seen
phosphorus burnt in the air, or in oxygen; and you have seen iron-filings
burnt in oxygen. But we have other tests besides these, and I am about to
refer to one or two of them for the purpose of carrying your conviction