honours me by her presence at these Lectures, has conferred a
still further obligation by sending me these two candles, which are from
Japan, and, I presume, are made of that substance to which I referred in a
former lecture. You see that they are even far more highly ornamented than
the French candles; and, I suppose, are candles of luxury, judging from
their appearance. They have a remarkable peculiarity about them--namely, a
hollow wick,--that beautiful peculiarity which Argand introduced into the
lamp, and made so valuable. To those who receive such presents from the
East, I may just say that this and such like materials gradually undergo a
change which gives them on the surface a dull and dead appearance; but
they may easily be restored to their original beauty, if the surface be
rubbed with a clean cloth or silk handkerchief, so as to polish the little
rugosity or roughness: this will restore the beauty of the colours. I have
so rubbed one of these candles, and you see the difference between it and
the other which has not been polished, but which may be restored by the
same process. Observe, also, that these moulded candles from Japan are
made more conical than the moulded candles in this part of the world.

I told you, when we last met, a good deal about carbonic acid. We found,
by the lime-water test, that when the vapour from the top of the candle or
lamp was received into bottles, and tested by this solution of lime-water
(the composition of which I explained to you, and which you can make for
yourselves), we had that white opacity which was in fact calcareous
matter, like shells and corals, and many of the rocks and minerals in the
earth. But I have not yet told you fully and clearly the chemical history
of this substance--carbonic acid--as we have it from the candle, and I
must now resume that subject. We have seen the products, and the nature of
them, as they issue from the candle. We have traced the water to its
elements, and now we have to see where are the elements of the carbonic
acid supplied by the candle. A few experiments will shew this. You
remember that when a candle burns badly, it produces smoke; but if it is
burning well, there is no smoke. And you know that the brightness of the
candle is due to this smoke, which becomes ignited. Here is an experiment
to prove this: so long as the smoke remains in the flame of the candle and
becomes ignited, it gives a beautiful light, and never appears to us i