One glimpse he caught of the nightmare-like forms clustered beyond the doorway, then a terrified cry burst from his lips.

“Great Heavens! What devils!”

He leapt to his feet, and at that, as though aroused to fresh fury by his movement, the river-creatures burst en masse through the doorway.

Never will Garth forget that terrible moment!

Often, long afterwards, he would awake, trembling in every limb, from some hideous dream, wherein he was once more at close grips with the loathsome inhabitants of the subterranean river.

The whole thing was a nightmare of glaring eyes and grabbing, misshapen limbs, and through it all the inventor, scarcely yet recovered from his long period of insensibility, was conscious of but one thing, the intermittent cracking of the millionaire’s weapons.

The turret was filled with smoke, through which the ghastly forms of the attackers loomed monstrous and terrible.

Suddenly the sound of Haverly’s revolvers ceased: his last chamber was empty!

But the creatures had had enough. Eight of their number lay dead, while two or three of the rest were badly wounded, and, obeying a common impulse, they dragged themselves through the doorway, shambled across the deck, and plunged overboard.

“Thank Heaven!” Haverly’s voice was a trifle shaky as he mopped his smoke-grimed brow.