under their feet.

"I once knew a mule who was so fond of music that he used to poke his
head into the window near which his master's daughter was playing on the
piano," said the Superintendent, who noticed their agitation and wanted
to amuse them. "We might get up band concerts for these fellows."

"Poor old things, I believe they would like it!" exclaimed Helen.

"This is a regular underground village," commented Mrs. Morton, as they
walked for a long distance through narrow passages until they found
themselves at the heading of a drift where the men were working.

"Is there any gas here?" asked the Superintendent, and when the miners
said "Yes," he lifted his hand light, which was encased in wire gauze,
and thrust it upwards toward the roof and gave a grunt as it flickered
near the top.

There it was, the dreaded fire-damp, in a layer above their heads. One
touch of an open flame and there would be a terrible explosion, yet the
miners were working undisturbed just beneath it with unprotected lamps
on their caps. The visitors felt suddenly like recruits under fire--they
were far from enjoying the situation but they did not want to seem
alarmed. No one made any protest, but neither did any one protest when
the Superintendent led the way to a section of the mine where there was
no gas that they might see a sight which he assured them was without
doubt wonderful.

They were glad that they had been assured that there was no fire-damp
here, for their leader lifted his lamp close to the roof. Ethel Blue
made the beginning of an exclamation as she saw his arm rising, but she
smothered her cry for her good sense told her that this experienced man
would not endanger the lives of himself or his guests. The coal had been
taken out very cleanly, and above them they saw not coal but shale.

"What is shale?" inquired Helen.

"Hardened clay," replied the Superintendent. "There were no men until
long after the carboniferous period when coal was formed, but just in
this spot it must have happened that the soil that had gathered above
the deposits of coal was very light for some reason or other. Above the
coal there was only a thin layer of soft clay. One day a hunter tramped
this way and left his autograph behind."

He held his lamp steadily upward, and there in the roof were the
unmistakable prints of the soles of a man's feet, walking.

"It surely does look mightily as if your explanation was correct,"
exclaimed Mr. Emers