But, before the old man could retort, Anton broke in.
"Father told me he's seen some, just like that. It was in Wales. A woman visitor had gone down to see the mine."
Otto shook his head gravely.
"Never a woman went down a coal mine yet, but an accident happened right after," he declared. "In the big explosion at Loosburg, when over four hundred miners were killed, it was found out, after, that one o' the miners was a woman who had dressed herself in men's clothes an' was pickin' coal. But what was it your father saw, Anton?"
"It happened right when the visiting party was in the mine," the boy explained. "It was in one of the main galleries, which was strongly timbered. A prop, which had been standing firmly for ever so many years, suddenly crumbled into splinters and the roof fell on the woman, hurting her so badly that she died soon after she was taken to the top.
"Just after the roof fell, so Father said, he and all the rest of the miners saw a band of knockers gathered around the pile of fallen roof and pointing at the figure of the woman crushed beneath. He said the knockers were laughing so loudly that some of the miners heard the echoes away at the other end of the mine."
"And do you believe that, Anton?" queried Clem, incredulously.
"Father saw them himself," the boy replied, in a tone of finality.
"Then there's the gas sprites," Otto went on, pleased at having found a sympathetic listener. "I've never seen 'em myself, but there's plenty that have. In a mine where I used to work, in Belgium, there was a man who could see 'em as plain as I see you or Anton. That was his job, and he was paid handsomely, too.
"He could walk through a gallery, either in a workin' or an abandoned mine, an' could tell right away if there was fire damp, or white damp, or black damp, or stink damp, in the workin's. He could see the gas sprites himself an' give warnin' where men had better not go. He didn't have to carry a safety lamp, nor chemical apparatus, nor cages of mice an' canaries, the way folks do, now. He just walked into the mine an' saw the sprites. He was friendly to 'em, an' they never did him no harm."