ches fire directly it is exposed to
the atmosphere (Fig. 21 _c_). There it is! Only powder the lead
sufficiently fine,--that is to say, bring it into a state of minute
subdivision,--and it fires by contact with the oxygen of the air. And
now apply this. We have in our diamond the element carbon, but
diamond-carbon is a hard substance, and not in a finely-divided state.
We have in this tinder the same substance as the diamond, but
tinder-carbon is finely divided, and it is because it is in a
finely-divided condition that the carbon in our tinder-box catches fire
so readily. I hope I have made that part of my subject quite clear to
you. I should wish you to note that this very finely-divided carbon has
rather an inclination to attract moisture. That is the reason why our
tinder is so disposed to get damp, as I told you; and, as damp tinder is
very difficult to light, this explains the meaning of those
disrespectful words that I suggested our tinder-box had often had
addressed to it in the course of its active life of service.

[Illustration: Fig. 21.]

But to proceed. What do I want now? I want a spark to fire my tinder. A
spark is enough. Do you remember the motto of the Royal Humane Society?
Some of my young friends can no doubt translate it, "Lateat scintilla
forsan"--perchance a spark may lie hid. If a person rescued from
drowning has but a spark of life remaining, try and get the spark to
burst into activity. That is what the motto of that excellent society
means. How am I to get this spark from the flint and steel to set fire
to my tinder? I take the steel in one hand, as you see, and I set to
work to strike it as vehemently as I can with the flint which I hold in
the other (Fig. 3 A B). Spark follows spark. See how brilliant they are!
But I want one spark at least to fall on my tinder. There, I have
succeeded, and it has set fire to my tinder. One spark was enough. The
spark was obtained by the collision of the steel and flint. The sparks
produced by this striking of flint against steel were formerly the only
safe light the coal-miner had to light him in his dark dreary work of
procuring coal. Here is the flint and steel lamp which originally
belonged to Sir Humphry Davy (Fig. 22). The miners could not use candles
in coal-mines because that would have been dangerous, and they were
driven to employ an apparatus consisting of an iron wheel revolving
against a piece of flint for the purpose of getting as much light