"The boiler!" shouted Stern.
Off he flung the head-piece. He leaped up; he seized the girl.
Out of the place he dragged her. She screamed as a huge weight from high aloft on the tower smashed bellowing through the roof, and with a shower of stones ripped its way down through the rubbish of the floors below, as easily as a bullet would pierce a newspaper.
The crash sent them recoiling. The whole roof shook and trembled like honey-combed ice in a spring thaw.
Down below, something rumbled, jarred, and came to rest.
Both of them expected nothing but that the entire structure would collapse like a card-house and shatter down in ruins that would be their death.
But though it swayed and quivered, as in the grasp of an earthquake, it held.
Stern circled Beatrice with his arm.
"Courage, now! Steady now, steady!" cried he.
The grinding, the booming of down-hurled stones and walls died away; the echoes ceased. A wind-whipped cloud of steam and smoke burst up, fanlike, beyond the edge of the roof. It bellied away, dim in the night, upon the stiff northerly breeze.
"Fire?" ventured the girl.
"No! Nothing to burn. But come, come; let's get out o' this anyhow. There's nothing doing, any more. All through! Too much risk staying up here, now."
Silent and dejected, they made their cautious way over the shaken roof. They walked with the greatest circumspection, to avoid falling through some new hole or freshly opened crevasse.
To Stern, especially, this accident was bitter. After nearly a fortnight's exhausting toil, the miserable fiasco was maddening.
"Look!" suddenly exclaimed the engineer, pointing. A vast, gaping canyon of blackness opened at their very feet--a yawning gash forty feet long and ten or twelve broad, with roughly jagged edges, leading down into unfathomed depths below.
Stern gazed at it, puzzled, a moment, then peered up into the darkness above.
"H-m!" said he. "One of the half-ton hands of the big clock up there has just taken a drop, that's all. One drop too much, I call it. Now if we--or our rooms--had just happened to be underneath? Some excitement, eh?"
They circled the opening and approached the tower wall. Stern picked up the rough ladder, which had been shaken down from its place, and once more set it to the window through which they were to enter.
But even as Beatrice put her foot on the first rung, she started with a cry. Stern felt the grip of her trembling hand on his arm.
"What is it?" exclaimed he.
"Look! Look!"
Immobile with astonishment and fear, she stood pointing out and away, to westward, toward the Hudson.