Alas! it was too late to fly! Old Silfax stood there, prepared to fulfill his last dreadful threat--prepared to stop the marriage of Nell and Harry by overwhelming the entire population of the place beneath the ruins of the coal mine.
As he stood ready to accomplish this act of vengeance, his enormous owl, whose white plumage was marked with black spots, was seen hovering directly above his head.
At that moment a man flung himself into the waters of the lake, and swam vigorously towards the canoe.
It was Jack Ryan, fully determined to reach the madman before he could do the dreadful deed of destruction.
Silfax saw him coming.

Instantly he smashed the glass of his lamp, and, snatching out the burning wick, waved it in the air.
Silence like death fell upon the astounded multitude.

James Starr, in the calmness of despair, marvelled that the inevitable explosion was even for a moment delayed.
Silfax, gazing upwards with wild and contracted features, appeared to become aware that the gas, lighter than the lower atmosphere, was accumulating far up under the dome; and at a sign from him the owl, seizing in its claw the lighted match, soared upwards to the vaulted roof, towards which the madman pointed with outstretched arm.
Another second and New Aberfoyle would be no more.
Suddenly Nell sprang from Harry's arms, and, with a bright look of inspiration, she ran to the very brink of the waters of the lake.
"Harfang! Harfang!" cried she in a clear voice; "here! come to me!" The faithful bird, surprised, appeared to hesitate in its flight.
Presently, recognizing Nell's voice, it dropped the burning match into the water, and, describing a wide circle, flew downwards, alighting at the maiden's feet.
Then a terrible cry echoed through the vaulted roofs.

It was the last sound uttered by old Silfax.
Just as Jack Ryan laid his hand on the edge of the canoe, the old man, foiled in his purpose of revenge, cast himself headlong into the waters of the lake.
"Save him! oh, save him!" shrieked Nell in a voice of agony.

Immediately Harry plunged into the water, and, swimming towards Jack Ryan, he dived repeatedly.
But his efforts were useless.