t in its
combination with the oxide of zinc, which is produced. I have now poured
the acid into the glass, and the effect is as though I were applying heat
to cause this boiling up. There is something coming off from the zinc very
abundantly, which is not steam. There is a jar full of it; and you will
find that I have exactly the same combustible substance remaining in the
vessel, when I hold it upside-down, that I produced during the experiment
with the iron barrel. This is what we get from water--the same substance
which is contained in the candle.

[Illustration: Fig. 16.]

Let us now trace distinctly the connection between these two points. This
is hydrogen--a body classed among those things which in Chemistry we call
elements, because we can get nothing else out of them. A candle is not an
elementary body, because we can get carbon out of it; we can get this
hydrogen out of it, or at least out of the water which it supplies. And
this gas has been so named hydrogen, because it is that element which, in
association with another, generates water. [Footnote: [greek: hudos],
"water," and [greek: gennao], "I generate."] Mr. Anderson having now been
able to get two or three jars of gas, we shall have a few experiments to
make, and I want to shew you the best way of making these experiments. I
am not afraid to shew you, for I wish you to make experiments, if you will
only make them with care and attention, and the assent of those around
you. As we advance in Chemistry, we are obliged to deal with substances
which are rather injurious, if in their wrong places--the acids, and heat,
and combustible things we use, might do harm if carelessly employed. If
you want to make hydrogen, you can make it easily from bits of zinc, and
sulphuric or muriatic acid. Here is what in former times was called the
"philosopher's candle." It is a little phial with a cork, and a tube or
pipe passing through it.

[Illustration: Fig. 17.]

And I am now putting a few little pieces of zinc into it. This little
instrument I am going to apply to a useful purpose in our
demonstrations--for I want to shew you that you can prepare hydrogen, and
make some experiments with it as you please at your own homes. Let me here
tell you why I am so careful to fill this phial nearly, and yet not quite
full. I do it because the evolved gas, which, as you have seen, is very
combustible, is explosive to a considerable extent when mixed with air,
and might lead to