"Ay, lad," said the old miner, the pale flame of his cap-lamp lighting up his wrinkled face and throwing a distorted shadow on the wall of coal behind, "there's goin' to be a plenty of us killed soon."

"Likely enough, if they're all as careless as you," Clem retorted.

"Carelessness ain't got nothin' to do with it," the old man replied. "The 'knockers' has got to be satisfied! There ain't been an accident here for months. It'll come soon! The spirits o' the mine is gettin' hungry for blood."

"Nonsense, Otto! The idea of an old-timer like you believing in goblins and all that superstitious stuff!"

"It's easy enough for you to say 'nonsense,' Clem Swinton, an' to make game o' men who were handlin' a coal pick when you was playin' with a rattle, but that don't change the facts. Why, even Anton, here, youngster that he is, knows better'n to deny the spirits below ground. The knockers got your father, Anton, didn't they?"

Anton Rover, one of the youngest boys in the mine, to whom the old miner had turned for affirmation, nodded his head in agreement. Like many of his fellows, the lad was profoundly credulous.

From his Polish mother—herself the daughter of a Polish miner—Anton had inherited a firm belief in demons, goblins, gnomes, trolls, kobolds, knockers, and the various races of weird creatures with which the Slavic and Teutonic peoples have dowered the world underground. From his earliest childhood he had been familiar with tales of subterranean terror, and he knew that his father had often foregone a day's work and a day's pay rather than go down the mine-shaft if some evil omen had occurred.

Yet Anton was willing to accept modern ideas, also. Clem was both his protector and his chum, and the boy had a great respect for his older comrade's knowledge and good sense. He was aware, too, that Clem was unusually well informed, for the young fellow was a natural student and was fitting himself for a higher position in the mine by hard reading. This Ohio mine, like many of the American collieries, maintained a free school and an admirable technical library for the use of those workers who wished to better themselves.

The young student miner was zealous in his efforts to promote modern ideas among his comrades, and knew that the old superstitions bred carelessness and a blind belief in Fate. Despite their differences in age and in points of view, he and Otto were warm friends, and he returned the old man's attack promptly.

"So far as Anton's father is concerned, Otto," he said, "it was Jim Rover's carelessness that killed him. He was caught by a falling roof just because he wouldn't take the trouble to make sure that the draw slate overhead was solid before setting to work to undercut the coal. I know that's so, because he told me, just before he died. I was the first one to reach him, after the fall, for I was working in the next room, just around the rib."

"An' who made the draw slate fall, just when Jim Rover was a-standin' right under it? Answer me that, Clem Swinton!"The other shrugged his shoulders.

"Every man who's ever handled a coal pick knows that draw slate is apt to work loose. That's one of the dangers of the business. And the danger can be avoided, as you know perfectly well, Otto, if a chap will feel the roof for vibration, with one hand, while he uses the other to tap on the slate with the flat side of a pick. If he won't take the trouble—why, it's his own fault if he gets killed.

"Blaming the 'knockers,' Otto, doesn't hide the fact that nearly a thousand miners get killed in the United States every year, just through their own carelessness."

The old man shook a finger ominously.

"It isn't always the careless ones what get taken," he declared. "Look out for yourself, Clem Swinton; look out for yourself! It's you the knockers'll be after, next, an' much good all your readin'll do you, then! I warned Jim Rover less'n a week afore he got killed, an' I'm warnin' you now."

Anton looked up, fearfully, for old Otto had a reputation as a seer, in the mine, but Clem only laughed."I put my faith in following out the safety rules, Otto," he replied, "not in charms and tricks to keep the goblins away."

The old man, however, was not thus to be set aside. He was as ready to defend his old-fashioned beliefs as was Clem to advance his modern theories.

"Experience goes for somethin'," he affirmed stubbornly. "Boy an' man, I've been below ground for over forty years. I've worked in Germany, Belgium, France, and all over this country. Just eight years old I was, when I went down the shaft for the first time; there weren't no laws, then, to keep youngsters out of a mine.

"I was a door-boy to start off with, openin' doors for the coal-cars to come through. That meant keeping one's ears open. The loaded cars come a-roarin' down the slopin' galleries, an', if a kid didn't hear them, he'd get smashed between the coal car an' the door. Even when he did hear them, he had to jump lively, or he'd get nipped, anyhow.

"On the other side o' the door it wasn't much better, for the empty cars were hauled up the slope o' the mine galleries by donkey power, an', if a kid didn't hear the whistle o' the donkey driver, he'd get his head clouted an' would be fined two days' pay beside.

"There warn't no eight-hours' day, then. We worked a shift o' twelve hours, an' the miners didn't stop between for meals—just took their grub in bites while they went on holin' coal. All piece-work it was in them days, an' every miner holed, spragged (or timbered), picked and loaded his own coal. The more stuff he got out, the more pay. The men didn't get any too much money, either, an' if a miner wanted to have a decent pay-check at the end o' the week, he warn't goin' to be hindered by havin' any trouble with cars. The poor kid at the door got it comin' to him from all sides.

"It's different now in coal-mines to what it was then. We hadn't no electric plant to run ventilatin' fans for keepin' the air fit to breathe. Nowadays, a man can be nigh as comfortable below ground as he can be above; but, when I was a kid, the air in a mine was hot, an' heavy, an' sleepy-like.

"After breathin' that air for nine or ten hours, it was hard to keep awake. You'd see the pit-boys comin' up out o' the shaft wi' their eyes all red an' swollen an' achin'. No, it warn't from gas, it was just from rubbin' em to keep em' open. An' rubbin' your eyes with hands all gritty with coal-dust ain't any too good for 'em."

"Well, Otto," the young fellow interrupted, "you can't deny that modern methods have improved all that. There aren't any door-boys in a modern mine. Most of the States in this country have passed laws requiring that all doors through which coal cars pass must be operated automatically. The United States Bureau of Mines keeps a sharp lookout, too. There aren't any donkeys, either, not in up-to-date mines; endless-chain conveyors take the coal from the face where the miner has dug it clear to the mouth of the shaft, and load it into the buckets by a self-tipping device. As for small boys in a mine, as you said yourself, there aren't any, not in the United States, anyhow."

"I'm not denyin' that minin' has got easier," was the grudging reply, "it'd be a wonder if it hadn't. What I'm sayin' is that all your newfangled schemes don't stop accidents and won't never stop accidents, not till you get rid o' the knockers an' gas sprites of a mine. An' that you'll never do!

"You're like a whole lot o' these young fellows, Clem, who believe nothin' that they don't see. You don't never stop to think that maybe it's your own blindness an' not your own cleverness that keeps you from seem'. Wait till I tell you what happened to me, one time, when I was a door-boy in Germany.

"Long afore I first went down into a coal mine, I knew about the knockers, and where they come from. Dad told me that all the coal-seams o' the world were forests, once. Long afore Noah an' the Flood. He'd seen ferns an' leaves o' trees turned into coal. One time, when digging out a seam, he'd come across the trunk of a tree standin' upright in the coal, with the roots still in the under clay."

"That's right enough," agreed Clem, "but the coal-forests were a good many million years older than Noah!"

"Maybe, maybe; but you warn't there to see," Otto retorted. "Anyhow, there were forests, an' these forests were standin' afore the Flood. Judgin' by what's left, the trees o' these forests must ha' been big."All those trees, Dad used to say, had spirits o' their own, just like trees have to-day. Elves an' dryads, he used to call 'em. When the Flood came an' spread deep water over the whole world, the tops o' the hills were washed into the valleys an' all these forests were covered in mud an' sand. That's how it is you never find anything but shale or slate (which is mud-rock) or sandstone above a coal seam. What's more, when pullin' down slate, you'll often find sea-shells, like mussels an' clams. Ain't that so?"

"I won't argue with you about the Flood, Otto, for that's a long story. But you're dead right in saying that all coal seams are overlaid with rocks which have been laid down by water, and that fossil shells are found in the overlying layers. But go ahead and tell us what you saw."

"When the Flood came," the old man resumed, "the elves an' dryads what used to live in the coal-trees were swallowed up in the water. They weren't drowned, because spirits can't die—at least, that was what Dad told me. They couldn't go away from their trees, because the trees were still standin' there, though all covered in mud or sand. So they had to change their ways for a new life, first under the water, an' when the waters o' the Flood dried up, under the ground. The elves, who were the men-spirits o' the forest, became knockers; the dryads, who were the women-spirits o' the trees, became the sprites o' the gas damps.

"In the old days, folks used to be able to see these spirits o' the forests. They used to build temples to 'em, an' have regular festivals in the woods, always leavin' some food for 'em to eat. Dad told me never to forget that the only way to keep on the good side o' the spirits below ground was to keep out o' the mine on the first day o' spring an' the last day o' summer, an' every time I took anything to eat below ground, to leave a bite behind.

"I've always done it. In all the years I've been minin', I've never gone down the shaft on March 21st or September 20th, an' I never will. An', every time I've taken my dinner-pail to the face where I was workin', I've put a bit o' bread aside for the knockers. You can believe it or not, as you like, but when I got back to the place, on my next shift, the bread was gone."

"Probably rats," commented Clem, in an aside to Anton.

The old miner paid no heed to the interruption, if, indeed, he heard it.

"That way, I always knew that the knockers were on my side, an' I've been willin' to hole coal in mines that folks said weren't safe. What's more, in forty years o' work, I've never lost a day's time from an accident of any kind. I know I'm safe, because of what happened to me when I was still a kid.

"One day—I don't know just why, maybe the air was worse'n usual—after I'd been lookin' after the door for the bigger part o' the shift, I dropped right off asleep. Half-dreamin', I heard a loaded car come roarin' down, but I didn't wake up until it was so close as to be too late.

"I scrambled up on my feet an' was just makin' a wild jump forward to the door, when I felt a little fist—it seemed about the size of a baby's, but was strong an' hard—hit me right in the chest. It pushed me back into the corner, out o' the way o' the car, an' held me there.

"At the same minute, an' just in the nick o' time, the door swung open.

"Rubbin' my eyes—they was so gritty wi' coal that I could hardly look out o' them—I saw what looked like a little man made o' coal standin' back against the door an' holdin' it open for the car to pass through. His face was sort o' pale, like a whitewashed wall in the dark, an' his eyes were red, like sparks. I thought he had a pointed hat an' long pointed shoes, but I was so scared that I couldn't be rightly sure. I could just see his whitish face movin' up an' down, like he was noddin' his head. Then the door slammed shut, the hand suddenly lifted off my chest an' I didn't see nothin' more. I tell you, I kept awake after that."

"You must have opened the door unconsciously, while half-asleep, and dreamed about seeing the goblin," was Clem's comment.

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."

"What were they like, Otto?" queried Anton.

"Shadows o' women," the old man replied promptly. "Fire damp, this diviner used to say, looked like a figure veiled in red, black damp was veiled in black wi' white edges, white damp was bluish, an' stink damp was yellow. When the gas was faint, all he could see was just the glow o' the colors, very dim; but when the gas was strong then the shapes o' the women were bold an' clear.

"The gas sprites, bein' women, catch an' hold the young men an' the single men more easily than old an' married miners. You don't deny that single men are more often killed by damps than married men, do you, Clem?"

The young miner looked uncomfortable at the question.

"That's a general belief, and statistics seem to back it up," he admitted. "But I don't see that it has anything to do with your goblin ideas, Otto. It's just because the single men, generally, are the youngest, and they haven't become as immune to the poisonous gases of the mine as men who have been working below ground all their lives."

"You can explain away anything, if you have a mind to," Otto retorted scornfully. "But as long as men are workin' below ground, there's goin' to be knockers an' sprites o' the damps, an' miners is goin' to be killed. Me, I've escaped. Why? Because I'm chock-full o' science an' modern ideas? Not a bit of it! I get along because I know what the spirits o' the mine expect, an' I give it to 'em. Right now, I'm the oldest man at work, here, an' I ain't never had an accident."

"Don't you believe his stories, Anton," the young miner protested, turning to the boy. "Those antiquated notions will only lead you astray. The 'damps' are just various kinds of gases coming out of the coal, and the way to fight them is to keep a strong current of air going through the mine."

"How do they come out o' the coal, if you know so much?" questioned Otto, belligerently.

"Sure I know! But I don't suppose telling you will change your ideas."

"It won't," the old miner admitted frankly. "But I've had my say, an' it's only fair to let you have yours. The youngster, here, can believe which o' the two he pleases."

"Well, it's something this way," Clem began, casting about in his mind for a way to explain the chemistry of mine air as simply as he could. "Ordinary air—the air above ground—is made up of a little less than 21 per cent. of oxygen and a little more than 78 per cent. of nitrogen. The rest of it is a mixture of carbon and oxygen which the books call carbon dioxide or black damp, with some other rare gases beside.

"Now, all animals, including man, depend for their life on the oxygen in the air. If the oxygen drops to 15 per cent., a man will suffer. That's not likely to happen where miners' lamps or safety-lamps are used, because the flame of a lamp goes out when there's less than 17 per cent. oxygen. Even at 19 per cent., a lamp will burn so dimly as to warn of danger. The nitrogen in the air is inert, that is, it does neither good nor harm to man. But what I want you to remember, Anton, is that even in the purest air above ground, there's always some 'black damp,' so it's a bit hard to see where Otto's goblin women come in!

"Now, when pure air comes down a coal shaft, a lot of changes happen to it. Some of the oxygen is consumed by the breathing of the men and animals in the mine—if there are any donkeys or such—some is taken up by the burning of lamps, some more by the explosion of blasting powder, a little is lost by the rusting of iron pyrites—which is found in many coal mines—and a lot of it is taken up by the coal, just how, we don't quite know."

"It's good to hear o' somethin' you don't know," the old miner remarked sarcastically. "But you're talkin' about dry air, an' the air in most mines is moist."

"Quite right," Clem agreed. "It has to be. Mine air is made moist, on purpose, especially in winter.""It is?" Otto's voice expressed unqualified astonishment.

"It certainly is! In most coal-mines—this one, for instance—all the air that passes down the intake shaft is moistened by a spray of mixed water and air, so finely atomized that it floats like a cloud."

"What for? It's easier to work in dry air'n moist air."

"It's easier to get blown up, too! In winter time, Otto, the air above ground is a lot colder than the air in the mine. Cold air can't hold as much moisture as warm air, and as soon as air gets warmed up a bit, it tries its hardest to absorb any moisture with which it happens to come in contact.

"What happens in a mine, in such a case? Why, as the cold air from above passes through the galleries of a mine, it gets warmed up. As it warms up, it draws out from the roofs, the ribs, and the floors all the water that there is to draw, and makes the mine dead dry. When coal dust is absolutely dry, it crumbles into finer and finer dust, until at last the particles are so small that they float in the air. Then comes disaster, for finely divided coal dust is so explosive that the smallest flame—even a spark from the stroke of a pick—will set the whole mine ablaze."

"I don't see that," interrupted Anton. "If dust is so bad, why do the bosses hang boards from all the gallery roofs and pile them high with dust?"

"Because the dust in those piles is stone dust, my boy," the young fellow explained. "When an explosion happens, it drives a big blast of air in front of it, so strong, sometimes, as to knock a man down. The blast of air blows all the stone dust from those boards and fills the air chock-full of it.

"This stone dust, usually made from crushed limestone or crushed shale, won't burn. The flame of the explosion can't pass through and the fire can't jump a rock-dust barrier. Even the flame of methane, which you know better as 'gas,' or fire damp, which has a terrific force, is choked back by this dense cloud of rock-dust, and, as you know, all coal mines have more or less methane gas."

"They don't, either," contradicted Otto. "I've worked in mines for years at a time an' never seen the 'cap' on the flame of the safety-lamp, tellin' there's fire damp there.""You may not have seen it, but there was gas there, just the same. As for the cap-flame you're talking about, Otto, I'll admit that it's the surest way of telling when there's so much fire-damp that the mine is getting dangerous. But it's a risky test, just the same. You can't see the little cap of methane gas flame burning above the oil flame of the lamp until there's 2 per cent. of gas in the air of the mine, and a little more than 5 per cent. will start an explosion."

"What makes that cap?" queried Anton.

"Fire damp or methane gas burning inside the wire gauze of the safety-lamp."

"But if the gas is already burning inside, why doesn't it explode outside?"

"Just because it's a safety-lamp, my boy. That's why the flame burns inside a wire gauze. I'll explain that.

"Suppose you take a lamp with a hot flame—an alcohol or spirit lamp will do—and light it. Then hold a piece of close-meshed wire gauze right on the flame. You'll find that the flame will spread under the wire gauze but will not go through. Hold it long enough, though, until the wire gets red hot, and, quite suddenly, the flame will pass through and burn above the gauze as well as below.

"Try another trick. Put out the lamp and then hold the gauze just where it was before. You can light the flame above the wire but it will not pass below the gauze until the wire gets red-hot. That shows that gas which is not burning can pass through a wire gauze, but that gas which is aflame cannot pass until the wire is red-hot."

"Yes," said Anton, "I can see that."

"Very good. Then, if you have a lamp which is burning inside a cylinder of wire gauze, the gas of fire-damp can go through, and, if there's enough of it to burn, it will burn above the flame of the lamp, making an aureole or 'cap' just as Otto says. But the flaming gas can't get back through the wire gauze to set fire to the fire-damp outside, at least, not until the wire gets red-hot, which it's not likely to do, seeing that the gas is in the middle, not underneath it.

"That's how they test for fire-damp, nowadays. The flame of a safety-lamp is drawn down until it shows only a small yellow tip. If there's any fire-damp in the air, a light-blue halo appears over the yellow flame. At a little more than 1 per cent., an experienced man can judge that there is gas there, but the true 'cap,' which is pointed like a cone, doesn't show until there's 2 per cent. of the gas. At 3 per cent., the cap will be like a dunce's cap, and more than half an inch high. At 4 per cent., it will be over an inch high, and at 4-1/2 per cent. it'll form a column of blue flame. Then it's high time to get out of the mine, and to get out quickly.

"In the improved form of safety-lamps, the oil flame burns inside a glass, but the air which reaches the flame has to pass through two cylinders of wire gauze. The glass keeps the flame from ever touching the innermost gauze, and, if an accident happens—such as the breaking of the glass—it would still be fairly safe, for the burning gas inside wouldn't pass through the inner gauze until that got red-hot, and it wouldn't reach the outer gauze because the current of air passing down between the two layers of wire mesh would keep the outer gauze cool. This safety-lamp was invented by Sir Humphry Davy, in England, in 1815, just after a big explosion in an English colliery had cost hundreds of lives. All mines nowadays require that miners use either safety-lamps or electric lamps, and it's every miner's business to report to the boss when he sees a cap of burning gas inside his safety-lamp."

The old miner nodded his head in agreement.

"I won't use an electric lamp," he commented. "It's foolishness. The gas sprites ain't really malicious. They're willin' enough to give a warnin'. They'll put a cap on a flame if they don't want folks in that part of the mine. An electric lamp tells nothin'. It won't even give a warnin' against black damp."

"Perfectly true," Clem agreed. "With an oil safety-lamp, the flame gets dim or even goes out if there's too much black damp. The electric lamp burns on, just the same, because the light is in a vacuum. Black damp isn't so dangerous as fire damp, though. It only causes distress and hard breathing because it shows that there's too big a proportion of nitrogen and carbon dioxide in the air and not enough oxygen. It's oxygen that a man misses."

"But black damp'll explode, too," put in Otto.

"No," the other corrected, "it won't. But it often happens that there's fire-damp around when black damp is present and the black damp makes a test for gas difficult. It's the gas that explodes, not the black damp."It isn't always the explosiveness of a damp that makes it dangerous, though," he went on. "As Otto could tell you, Anton, white damp is the worst of the three. And it doesn't give any warning at all."

"That's why we had that diviner in a Belgian mine," the old man commented, gravely. "He could see the gas sprites in their blue veils. But, if there's a lot o' white damp, you can tell it by the flame of a safety-lamp gettin' a little longer an' brighter."

"It's not safe to trust it," the young fellow advised. "You'd have trouble seeing 2 per cent, of white damp, and you'd be dead before you had much chance to look. Even with 1-1/2 per cent., a man would be likely to drop before he reached a better-ventilated part of the mine, and he couldn't see that much on the flame of his safety-lamp at all. To breathe the air with only 1 per cent. of white damp for an hour would put a man in such a state that he mightn't recover, and he wouldn't have had any warning.

"Luckily, there's much less danger of white damp in mines than there used to be. It's a gas that's formed only when there's been something burning. After an explosion in a mine, or a fire, there's sure to be a lot of it, and rescue parties have always found it their worst foe. But, in the ordinary working mine, it is rare."

"Not so rare as all that!" objected Otto. "We used to have a lot of it, on the other side."

"You wouldn't now," was the reply. "The white damp of those days was due to the heavy charges of gunpowder or low explosive that were used, explosives which are forbidden now in dangerous mines."

"They were better'n the stuff we use nowadays," grumbled Otto, "they brought down more coal an' didn't smash it up so bad."

"They smashed up men, instead," Clem retorted. "And they put a whole lot of white damp into a mine. That was really dangerous, because, in those days, people hadn't found out the value of canaries."

"I've often wondered about that," interjected Anton. "Why do the testing-parties carry canaries?"

"Because," answered Clem, with a smile, "canaries are as clever at seeing the gas sprites as was the Belgian diviner that Otto talks about. No, but seriously," he went on, "the reason is that canaries are extremely susceptible to white damp. Less than 1/4 of one per cent of white damp will cause a canary to collapse at once, and a man could breath that proportion for an hour without much harm. Even a tenth of one per cent. will cause the little bird to show signs of distress."

"It's tough on the bird," was Anton's sympathetic comment.

"Not especially! As soon as a bird begins to show collapse, it is taken back to the open air and is as frisky and lively as ever in five minutes. But its value as a warning signal is enormous, for it tells rescue parties or investigating parties when to put on gas masks or breathing apparatus containing oxygen. In a well-ventilated mine, however, where high explosive is used and handled by experienced men, there's not likely to be much danger from white damp.

"Stink damp is rare but can sometimes be dangerous. Generally, a fellow is warned away, because of the smell—which is just like rotten eggs. The worst part of stink damp is that it smells the worst when there's only a little of it. When there's so much of it around as to be deadly, it doesn't smell any worse. You get small quantities of it, sometimes, in blasting, but generally hydrogen sulphide or stink damp is found after a mine fire or an explosion. Rescue parties generally carry a cage of mice as well as one of canaries."

"With the same idea?" queried Anton.

"Exactly. As little as a tenth of one per cent. of stink damp makes a mouse sprawl on his belly, his legs don't seem strong enough to hold him up; while, in the same air, a canary doesn't suffer a bit.

"The only real danger in stink damp is when there's water in the mine, for example when, after a fire, a lot of water has been pumped down into the workings to put the fire out. Water absorbs stink damp very easily and gives it up equally easily when stirred. So, if a member of a rescue party puts his foot in a puddle of water where there has been stink damp around, so much of the gas may suddenly come up in his face as to topple him over.

"But you can see, Anton, that most of the gas troubles in a mine come from the blasting. That's why, nowadays, the miners who get out the coal seldom or never fire the shots. Experienced men, trained especially for that work, are used. After a miner has undercut the coal, the shot-firer comes. He tests for gas before he begins work, bores a deep hole in the coal with a drill, tests for gas again in case he should have tapped a leak in the seam, cleans out the hole, sends the miner for the box of explosive—which is kept thirty or forty yards away from the face where the coal is being cut—and prepares the charge with a detonater which he carries in a box over his shoulder. The miner never touches either the explosive or the detonater. Then the shot-firer puts the primed charge in the hole, jams the hole full of clay with a wooden tamper—a steel bar might cause a spark and a premature explosion—tests for gas again, connects the electric wires from a portable battery around the rib corner, fires the shot, returns to the face and tests for gas again. Then, and not until then, does the miner begin to dig the coal. That way, every one in the mine is safe."

"Yes," growled the old miner, "and the shot-firer doesn't dig any coal, nor do any hard work, an' gets paid more'n we do."

"He knows more than you do," Clem responded, "and he gets better pay because his experience and prudence is worth a lot of money to the mine. Just think what an explosion costs—to say nothing of the risk of lives being lost! And you won't find experienced shot-firers or mine-managers talking about gas sprites, Otto!"

"Better for 'em if they did!" the old man warned. "For I'm sayin' to you again, what I said before—the spirits o' the mine is gettin' hungry for blood!"