in the jars; but when you let a
candle down in, in some it burns just the same as before; in some it
burns brighter; and in some it goes out."

"In what kinds does it go out?" asked Rollo.

"I only know of one kind," said Jonas, "and that is a kind that comes of
itself in mines, and wells, and other places."

"What is the name of it?" asked Rollo.

"Why, the people in the mines call it choke damp; but I believe it has
got another name besides."

"What do they call it choke damp for?" said Rollo.

"Because," said Jonas, "if the miners get into it and breathe it, it
kills them. It is not any better to breathe than it is to make fires
burn."

"I wish I could see some choke damp," said Rollo.

"O, you can't see it at all," said Jonas, "if it was right before you,
any more than you can see common air. If a well or a mine is full of it,
they cannot find it out by looking down."

"How do they find it out?" said Rollo.

"Why, they let a candle down," replied Jonas.

"And will the candle go out?" asked Rollo.

"Yes," said Jonas, "if there is choke damp in the well. Sometimes they
make a little of it in a tumbler or a jar upon the table, and so let a
little flame down into it, and it goes out immediately."

"I wish we could make some," said Rollo. "Do you know how they make it?"

"No," said Jonas; "but I believe it is pretty easy to do it, if we only
knew how."

"I will ask my father," said Rollo; "perhaps he will know."

This conversation took place when Jonas and Rollo were about the fires;
but now the fires had pretty nearly burnt out, and they prepared to go
home.

That evening, just about sunset, Rollo went out behind the house, and
found Jonas raking off the yard. The spring was fast coming on, and the
grass was beginning to look a little green; and Jonas said he wanted to
get off all the sticks, chips, and straws, so that the yard would
present a surface of smooth and uniform green. Rollo told him that he
had found out how to make choke damp.

"Did your father tell you?" said Jonas.

"No," replied Rollo.

"Who did tell you, then?" said Jonas.

"Guess," answered Rollo.

"Your mother," said Jonas.

"No," answered Rollo.

"Then I can't tell," said Jonas.

"It was Miss Mary," replied Rollo. "I met her in the road to-day, and I
asked her."

"And how is it?" asked Jonas.

"Why, we make it with chalk and vinegar," said Rollo. "We pound up a
little chalk, and put it in the bottom of a tumbler.