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.
