ar and he willingly agreed to show them through. Before entering
the mine he pointed out to them samples of coal which he had collected.
Some had fern leaves plainly visible upon their surfaces and others
showed leaves of trees and shrubs.

"Fairy pencilings, a quaint design,
Veinings, leafage, fibers clear and fine,"

quoted Ethel Blue softly, as she looked at them.

Mrs. Morton stopped before a huge block of coal weighing several tons
and said to her son, "Here's a lump for your furnace, Roger."

"Phew," said Roger. "Think of a furnace large enough to fit that lump!
Do you get many of them?" he asked of the Superintendent.

"We keep that," said the Superintendent, "because it's the largest
single lump of coal ever brought out of this mine. Of course, we could
get them if we tried to, but it's easier to handle it in smaller
pieces."

"What'th in that little houthe over there?" asked Dicky. "Theems to me I
thee something whithing round."

"That's the fan that blows fresh air into the mine so that the miners
can breathe, and drives out the poisonous and dangerous gases."

"What would happen if the fan stopped running?" asked Ethel Brown.

"Many things might happen," said the Superintendent gravely. "Men might
suffocate for lack of air, or an explosion might follow from the
collection of the dreaded 'fire damp' ignited by some miner's lamp."

"Fire damp?" repeated Mrs. Morton. "That is really natural gas, isn't
it?"

"Yes, they're both 'marsh gas' caused by the decay of the huge ferns and
plants of the carboniferous age. Some of them hardened into coal and
others rotted when they were buried, and the gas was caught in huge
pockets. It is gas from these great pockets that people use for heating
and cooking all about here and even up into Canada."

Ethel Brown had been listening and the words "some of them hardened into
coal" caught her ear. She went close to her grandfather's side.

"Tell me," she said, "exactly what is coal and how did it get here?"

"What _I_ want to know," retorted Mr. Emerson, "is what brand of
curiosity you have in your cranium, and how did it get there? Answer me
that."

Ethel Brown laughed.

"Let's have a lecture," she urged, "and," handing her grandfather a
small lump of coal, "here's your text."

Mr. Emerson turned the bit of coal over and over.

"When I look at this little piece of black stone," he said, "I seem to
see dense forests filled with luxuriant foliage and