When they had got about half-way through it was thought best to close the outer end of the heading with an air-tight door, and place another ten feet behind it, thus forming an airlock. Fresh air was forced into and compressed in the heading by means of an air-pump operated from the flat-boat at the outer end. These precautions were taken for fear lest when they broke through into the breast the air in it, compressed by the flood, should rush out with destructive force. It was also feared that, relieved from its air pressure, the water in the breast would rise and cut off the escape of any persons who might be in there.
The position of those engaged in the work of rescue was by no means free from peril. The pumps, running at fullest speed, were barely able to keep the water from rising and flooding the new heading, so great and continuous was the flow into the mine from the soaked earth above it. They did not know but that any moment some fresh and unsuspected accumulation in the old workings might break forth and send a second flood pouring in upon them. Above all there was an ever-present danger from foul gases, which formed so rapidly that at times work had to be entirely suspended until they could be cleared away. Thus every time the relief men went down to their self-imposed labor their departure was watched by anxious women with tearful eyes and heavy hearts.
For a day and a night these stout-hearted men worked without knowing whether they sought the living or the dead. On the afternoon of the second day, during a momentary pause in the steady rattle of the picks, Jack Hobson, who was at the inner end of the heading, thought he heard a knocking. Calling for perfect silence, he listened. Yes, it was! Faint, but unmistakable, it came again.
"Tap, tap, tap; tap, tap, tap; tap, tap, tap," and a pause. Then it was repeated, and its meaning could not be doubted. As plain as human speech, it said,
"Here we are, still alive, but in great distress. We know you are coming, but you must hurry."
From mouth to mouth the joyful news was carried out from the heading, across the sullen waters, up the slope to the anxious waiting throngs, and on throbbing wires throughout the length and breadth of the land.
Mrs. Sterling heard it and lifted her tear-stained face in earnest thankfulness to Heaven. The Halfords heard it in Philadelphia, and Mr. Halford said he could stand it no longer, but must go to Raven Brook and be on hand when the men were rescued. Before another sun rose that faint tapping made in the recesses of the drowned mine by Derrick Sterling with a bit of rock had been heard around the world.
Now the brave fellows in the heading knew what they were working for, and the blows of their picks fell faster and harder than ever on the glistening wall that still opposed its black front to them.
The excitement at the mouth of the mine was now intense, and every man who came up from it was besieged by anxious inquiries for the very latest news. What was the meaning of the three taps three times repeated? Did it signify that there were nine persons in the breast, or only three? If only three, where were the others? Who were the three? How many were alive? Were any dead? These and a thousand like questions were asked and discussed, but nobody could answer them certainly.
The reports brought up were only regarding the progress of the work. So many feet in an hour, so many yards a day. Now there are only six feet more to cut through; now five, four, three, and now but eighteen inches. The suspense is terrible. To the mothers and wives waiting for the end up in the little village it is almost too great to be borne. To the haggard men behind those eighteen inches of black rock it seems as though the breath of fresh air for want of which they are dying would come too late.