Was this the water of the melted ice or was it that which filled the valley? Had their outer door stood firm or had it cracked or shrivelled up under the heat of the furnace through which the earth had passed? It flowed for ten minutes and then slackened and stopped. The outer door had held fast. Then, in case of accidents, the middle one was lowered again and they waited until the waters should have sufficiently subsided to enable them to challenge the last hazard on which their fate depended.
The sluice-gate had been raised at what would be four o’clock on the morning of the 26th of September, if the cataclysm through which the earth had passed had not so far affected the terrestrial economy as to alter the relations of day and night. Twelve hours later the pressure-gauge ceased to act, showing that the rapidly-sinking waters of the lake had reached the threshold of the outer door. The time had now come to ask the question on the answer to which the lives of the remnant of humanity depended—was the atmosphere breathable or not?
That was the one question which occupied, to the momentary exclusion of all others, the mind of every Aerian who was in the caverns. The middle gate was lifted, and every heart stood still as Alan and Alexis strode forward into the dark passage and grasped the levers which actuated the lifting mechanism of the outer one.
They took one glance back at the anxious faces which showed so white in the gleam of the electric lamps, and then they pulled. The machinery creaked and groaned as the power was applied. Then came a rending sound and a dull crash. The door lifted a little, quivered and dropped again, and remained immovable.
“The machinery has broken down!” said Alan, going back into the gallery. “There must have been a land-slip over the doorway.”
“What will you do then?” said Alma. “Surely we have not escaped the conflagration of the world to be buried alive after all!”
“No,” he said, looking down at her with a reassuring smile. “It can hardly be as bad as that. Unless a whole mountain has fallen in front of the door, we shall soon find a way out.”
The first thing to be done was to get rid of the door, and this Alan accomplished in summary fashion by undermining it with drills, and then, after he had sent everyone into the inner recesses of the caverns, tearing it to fragments with a small quantity of the explosive used in the shells.
A mass of earth and stones came rolling into the gallery immediately after the explosion, then an excavating machine was run up on hastily-laid rails and was soon boring its way into the obstructing mass. A distance of ten yards was tunnelled and then there was a rattle and whir in front of the machine, which told that the work was done. There was a cloud of dust from pulverised stones and earth and then came a rush of fresh warm air and a gleam of sunlight through the opening.
“Thank God the atmosphere is still there and the sun is still shining!” cried Alan, as he drew the machine back and ran out into the open air.