ue to Mr. Tennant.

Now let us try to make some carbonic acid. --Will you, Emily, decant
some oxygen gas from this large jar into the receiver in which we are to
burn the carbon; and I shall introduce this small piece of charcoal,
with a little lighted tinder, which will be necessary to give the first
impulse to the combustion.

EMILY.

I cannot conceive how so small a piece of tinder, and that but just
lighted, can raise the temperature of the carbon sufficiently to set
fire to it; for it can produce scarcely any sensible heat, and it hardly
touches the carbon.

MRS. B.

The tinder thus kindled has only heat enough to begin its own
combustion, which, however, soon becomes so rapid in the oxygen gas, as
to raise the temperature of the charcoal sufficiently for this to burn
likewise, as you see is now the case.

EMILY.

I am surprised that the combustion of carbon is not more brilliant; it
does not give out near so much light or caloric as phosphorus, or
sulphur. Yet since it combines with so much oxygen, why is not a
proportional quantity of light and heat disengaged from the
decomposition of the oxygen gas, and the union of its electricity with
that of the charcoal?

MRS. B.

It is not surprising that less light and heat should be liberated in
this than in almost any other combustion, since the oxygen, instead of
entering into a solid or liquid combination, as it does in the
phosphoric and sulphuric acids, is employed in forming another elastic
fluid; it therefore parts with less of its caloric.

EMILY.

True; and, on second consideration, it appears, on the contrary,
surprising that the oxygen should, in its combination with carbon,
retain a sufficient portion of caloric to maintain both substances in a
gaseous state.

CAROLINE.

We may then judge of the degree of solidity in which oxygen is combined
in a burnt body, by the quantity of caloric liberated during its
combustion?

MRS. B.

Yes; provided that you take into the account the quantity of oxygen
absorbed by the combustible body, and observe the proportion which the
caloric bears to it.

CAROLINE.

But why should the water, after the combustion of carbon, rise in the
receiver, since the gas within it retains an aeriform state?

MRS. B.

Because the carbonic acid gas is gradually absorbed by the water; and
this effect would be promoted by shaking the receiver.

EMILY.

The charcoal is now extinguished, though it is not nearly cons