has been washed in water and deprived of its coarser particles, and so
supplied to the plasterer as whitening. Here is a large jar containing
this whitening and water, and I have here some strong sulphuric acid,
which is the acid you might have to use if you were to make these
experiments (only, in using this acid with limestone, the body that is
produced is an insoluble substance, whereas the muriatic acid produces a
soluble substance that does not so much thicken the water). And you will
seek out a reason why I take this kind of apparatus for the purpose of
shewing this experiment. I do it because you may repeat in a small way
what I am about to do in a large one. You will have here just the same
kind of action; and I am evolving in this large jar carbonic acid, exactly
the same in its nature and properties as the gas which we obtained from
the combustion of the candle in the atmosphere. And no matter how
different the two methods by which we prepare this carbonic acid, you will
see, when we get to the end of our subject, that it is all exactly the
same, whether prepared in the one way or in the other.

We will now proceed to the next experiment with regard to this gas. What
is its nature? Here is one of the vessels full, and we will try it, as we
have done so many other gases, by combustion. You see it is not
combustible, nor does it support combustion. Neither, as we know, does it
dissolve much in water, because we collect it over water very easily.
Then, you know that it has an effect, and becomes white in contact with
lime-water; and when it does become white in that way, it becomes one of
the constituents to make carbonate of lime or limestone.

The next thing I must shew you is, that it really does dissolve a little
in water, and therefore that it is unlike oxygen and hydrogen in that
respect I have here an apparatus by which we can produce this solution. In
the lower part of this apparatus is marble and acid, and in the upper part