"
"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 shrubbery and
mammoth trees under which move sluggish streams draining the swampy
ground. The air is damp and heavy and warm."
"What about the animals?"
"There are few animals. Most of them are water creatures, though there
are a few that can live on land and in the water, too, and in the latter
part of the coal-making period enormous reptiles crawled over the wet
floor of the forest.
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