at harry's call, james starr, madge, and simon ford entered through the narrow orifice which put the dochart pit in communication with the new mine. they found themselves at the beginning of a tolerably wide gallery. one might well believe that it had been pierced by the hand of man, that the pick and mattock had emptied it in the working of a new vein. the explorers question whether, by a strange chance, they had not been transported into some ancient mine, of the existence of which even the oldest miners in the county had ever known.

no! it was merely that the geological layers had left this passage when the secondary earths were in course of formation. perhaps some torrent had formerly dashed through it; but now it was as dry as if it had been cut some thousand feet lower, through granite rocks. at the same time, the air circulated freely, which showed that certain natural vents placed it in communication with the exterior atmosphere.

this observation, made by the engineer, was correct, and it was evident that the ventilation of the new mine would be easily managed. as to the fire-damp which had lately filtered through the schist, it seemed to have been contained in a pocket now empty, and it was certain that the atmosphere of the gallery was quite free from it. however, harry prudently carried only the safety lamp, which would insure light for twelve hours.

james starr and his companions now felt perfectly happy. all their wishes were satisfied. there was nothing but coal around them. a sort of emotion kept them silent; even simon ford restrained himself. his joy overflowed, not in long phrases, but in short ejaculations.

it was perhaps imprudent to venture so far into the crypt. pooh! they never thought of how they were to get back.

the gallery was practicable, not very winding. they met with no noxious exhalations, nor did any chasm bar the path. there was no reason for stopping for a whole hour; james starr, madge, harry, and simon ford walked on, though there was nothing to show them what was the exact direction of this unknown tunnel.

and they would no doubt have gone farther still, if they had not suddenly come to the end of the wide road which they had followed since their entrance into the mine.

the gallery ended in an enormous cavern, neither the height nor depth of which could be calculated. at what altitude arched the roof of this excavation--at what distance was its opposite wall--the darkness totally concealed; but by the light of the lamp the explorers could discover that its dome covered a vast extent of still water--pond or lake--whose picturesque rocky banks were lost in obscurity.

"halt!" exclaimed ford, stopping suddenly. "another step, and perhaps we shall fall into some fathomless pit."

"let us rest awhile, then, my friends," returned the engineer. "besides, we ought to be thinking of returning to the cottage."

"our lamp will give light for another ten hours, sir," said harry.

"well, let us make a halt," replied starr; "i confess my legs have need of a rest. and you, madge, don't you feel tired after so long a walk?"

"not over much, mr. starr," replied the sturdy scotchwoman; "we have been accustomed to explore the old aberfoyle mine for whole days together."

"tired? nonsense!" interrupted simon ford; "madge could go ten times as far, if necessary. but once more, mr. starr, wasn't my communication worth your trouble in coming to hear it? just dare to say no, mr. starr, dare to say no!"

"well, my old friend, i haven't felt so happy for a long while!" replied the engineer; "the small part of this marvelous mine that we have explored seems to show that its extent is very considerable, at least in length."

"in width and in depth, too, mr. starr!" returned simon ford.

"that we shall know later."

"and i can answer for it! trust to the instinct of an old miner! it has never deceived me!"

"i wish to believe you, simon," replied the engineer, smiling. "as far as i can judge from this short exploration, we possess the elements of a working which will last for centuries!"

"centuries!" exclaimed simon ford; "i believe you, sir! a thousand years and more will pass before the last bit of coal is taken out of our new mine!"

"heaven grant it!" returned starr. "as to the quality of the coal which crops out of these walls?"

"superb! mr. starr, superb!" answered ford; "just look at it yourself!"

and so saying, with his pick he struck off a fragment of the black rock.

"look! look!" he repeated, holding it close to his lamp; "the surface of this piece of coal is shining! we have here fat coal, rich in bituminous matter; and see how it comes in pieces, almost without dust! ah, mr. starr! twenty years ago this seam would have entered into a strong competition with swansea and cardiff! well, stokers will quarrel for it still, and if it costs little to extract it from the mine, it will not sell at a less price outside."

"indeed," said madge, who had taken the fragment of coal and was examining it with the air of a connoisseur; "that's good quality of coal. carry it home, simon, carry it back to the cottage! i want this first piece of coal to burn under our kettle."

"well said, wife!" answered the old overman, "and you shall see that i am not mistaken."

"mr. starr," asked harry, "have you any idea of the probable direction of this long passage which we have been following since our entrance into the new mine?"

"no, my lad," replied the engineer; "with a compass i could perhaps find out its general bearing; but without a compass i am here like a sailor in open sea, in the midst of fogs, when there is no sun by which to calculate his position."

"no doubt, mr. starr," replied ford; "but pray don't compare our position with that of the sailor, who has everywhere and always an abyss under his feet! we are on firm ground here, and need never be afraid of foundering."

"i won't tease you, then, old simon," answered james starr. "far be it from me even in jest to depreciate the new aberfoyle mine by an unjust comparison! i only meant to say one thing, and that is that we don't know where we are."

"we are in the subsoil of the county of stirling, mr. starr," replied simon ford; "and that i assert as if--"

"listen!" said harry, interrupting the old man. all listened, as the young miner was doing. his ears, which were very sharp, had caught a dull sound, like a distant murmur. his companions were not long in hearing it themselves. it was above their heads, a sort of rolling sound, in which though it was so feeble, the successive crescendo and diminuendo could be distinctly heard.

all four stood for some minutes, their ears on the stretch, without uttering a word. all at once simon ford exclaimed, "well, i declare! are trucks already running on the rails of new aberfoyle?"

"father," replied harry, "it sounds to me just like the noise made by waves rolling on the sea shore."

"we can't be under the sea though!" cried the old overman.

"no," said the engineer, "but it is not impossible that we should be under loch katrine."

"the roof cannot have much thickness just here, if the noise of the water is perceptible."

"very little indeed," answered james starr, "and that is the reason this cavern is so huge."

"you must be right, mr. starr," said harry.

"besides, the weather is so bad outside," resumed starr, "that the waters of the loch must be as rough as those of the firth of forth."

"well! what does it matter after all?" returned simon ford; "the seam won't be any the worse because it is under a loch. it would not be the first time that coal has been looked for under the very bed of the ocean! when we have to work under the bottom of the caledonian canal, where will be the harm?"

"well said, simon," cried the engineer, who could not restrain a smile at the overman's enthusiasm; "let us cut our trenches under the waters of the sea! let us bore the bed of the atlantic like a strainer; let us with our picks join our brethren of the united states through the subsoil of the ocean! let us dig into the center of the globe if necessary, to tear out the last scrap of coal."

"are you joking, mr. starr?" asked ford, with a pleased but slightly suspicious look.

"i joking, old man? no! but you are so enthusiastic that you carry me away into the regions of impossibility! come, let us return to the reality, which is sufficiently beautiful; leave our picks here, where we may find them another day, and let's take the road back to the cottage."

nothing more could be done for the time. later, the engineer, accompanied by a brigade of miners, supplied with lamps and all necessary tools, would resume the exploration of new aberfoyle. it was now time to return to the dochart pit. the road was easy, the gallery running nearly straight through the rock up to the orifice opened by the dynamite, so there was no fear of their losing themselves.

but as james starr was proceeding towards the gallery simon ford stopped him.

"mr. starr," said he, "you see this immense cavern, this subterranean lake, whose waters bathe this strand at our feet? well! it is to this place i mean to change my dwelling, here i will build a new cottage, and if some brave fellows will follow my example, before a year is over there will be one town more inside old england."

james starr, smiling approval of ford's plans, pressed his hand, and all three, preceding madge, re-entered the gallery, on their way back to the dochart pit. for the first mile no incident occurred. harry walked first, holding his lamp above his head. he carefully followed the principal gallery, without ever turning aside into the narrow tunnels which radiated to the right and left. it seemed as if the returning was to be accomplished as easily as the going, when an unexpected accident occurred which rendered the situation of the explorers very serious.

just at a moment when harry was raising his lamp there came a rush of air, as if caused by the flapping of invisible wings. the lamp escaped from his hands, fell on the rocky ground, and was broken to pieces.

james starr and his companions were suddenly plunged in absolute darkness. all the oil of the lamp was spilt, and it was of no further use. "well, harry," cried his father, "do you want us all to break our necks on the way back to the cottage?"

harry did not answer. he wondered if he ought to suspect the hand of a mysterious being in this last accident? could there possibly exist in these depths an enemy whose unaccountable antagonism would one day create serious difficulties? had someone an interest in defending the new coal field against any attempt at working it? in truth that seemed absurd, yet the facts spoke for themselves, and they accumulated in such a way as to change simple presumptions into certainties.

in the meantime the explorers' situation was bad enough. they had now, in the midst of black darkness, to follow the passage leading to the dochart pit for nearly five miles. there they would still have an hour's walk before reaching the cottage.

"come along," said simon ford. "we have no time to lose. we must grope our way along, like blind men. there's no fear of losing our way. the tunnels which open off our road are only just like those in a molehill, and by following the chief gallery we shall of course reach the opening we got in at. after that, it is the old mine. we know that, and it won't be the first time that harry and i have found ourselves there in the dark. besides, there we shall find the lamps that we left. forward then! harry, go first. mr. starr, follow him. madge, you go next, and i will bring up the rear. above everything, don't let us get separated."

all complied with the old overman's instructions. as he said, by groping carefully, they could not mistake the way. it was only necessary to make the hands take the place of the eyes, and to trust to their instinct, which had with simon ford and his son become a second nature.

james starr and his companions walked on in the order agreed. they did not speak, but it was not for want of thinking. it became evident that they had an adversary. but what was he, and how were they to defend themselves against these mysteriously-prepared attacks? these disquieting ideas crowded into their brains. however, this was not the moment to get discouraged.

harry, his arms extended, advanced with a firm step, touching first one and then the other side of the passage.

if a cleft or side opening presented itself, he felt with his hand that it was not the main way; either the cleft was too shallow, or the opening too narrow, and he thus kept in the right road.

in darkness through which the eye could not in the slightest degree pierce, this difficult return lasted two hours. by reckoning the time since they started, taking into consideration that the walking had not been rapid, starr calculated that he and his companions were near the opening. in fact, almost immediately, harry stopped.

"have we got to the end of the gallery?" asked simon ford.

"yes," answered the young miner.

"well! have you not found the hole which connects new aberfoyle with the dochart pit?"

"no," replied harry, whose impatient hands met with nothing but a solid wall.

the old overman stepped forward, and himself felt the schistous rock. a cry escaped him.

either the explorers had strayed from the right path on their return, or the narrow orifice, broken in the rock by the dynamite, had been recently stopped up. james starr and his companions were prisoners in new aberfoyle.