But first we will let Analysis tell us what chalk is made of, as far as he knows.
He will say--Chalk is carbonate of lime.
But what is carbonate of lime made of?
Lime and carbonic acid.
And what is lime?
The oxide of a certain metal, called calcium.
What do you mean?
That quicklime is a certain metal mixed with oxygen gas; and slacked lime is the same, mixed with water.
So lime is a metal.

What is a metal?
Nobody knows.
And what is oxygen gas?
Nobody knows.
Well, Analysis, stops short very soon.

He does not seem to know much about the matter.
Nay, nay, you are wrong there.

It is just "about the matter" that he does know, and knows a great deal, and very accurately; what he does not know is the matter itself.

He will tell you wonderful things about oxygen gas--how the air is full of it, the water full of it, every living thing full of it; how it changes hard bright steel into soft, foul rust; how a candle cannot burn without it, or you live without it.