There was cause for the old scientist’s excitement. An absolutely unknown world lay before them, untrodden--for aught they knew--by any human foot, a world whose stupendous size was veiled as yet from their knowledge by its weird and ghostly twilight. Above them the gloom hung thick as a funeral pall, a dense eternal canopy of midnight darkness. How far down they were beneath the earth’s surface they dared not think. Sufficient for them to know that, somewhere above them, perhaps thousands upon thousands of feet, was the vast dome which formed the inner roof of this subterranean world. They could but stare upward into the darkness, open-mouthed, and marvel at the immensity of it all. The weird growths ashore puzzled them not a little, even Mervyn for a while being perplexed to give a name to the things. Fleshy as a cactus, and having a somewhat similar branching habit of growth, each glowed throughout its entire length, as though an electric bulb were hidden within its pulpy heart. The things were weirdly beautiful as they towered there--many of them over twenty feet in height--flashing a rainbow-hued challenge to the great arc lamp of the _Seal._ They were Nature’s own illuminants, without which this underworld would have been dark as Hades. Suddenly a cry came from Mervyn. “I have it!” he cried. “They are fungi--luminous fungi!” “Fungi!” exclaimed his comrades in a breath. “Luminous fungi!” repeated the scientist triumphantly, “but of such vast size that they more nearly resemble trees. If we ever succeed in making our way back to civilisation our news will astonish the world.” “I don’t know,” Garth murmured. “It seems to me that you will have great difficulty in getting anyone to believe your statements. For instance, who will believe that the interior of the globe is hollow and contains an immense sea, and probably a great continent. See, there is a range of hills.” It was true. Far away in the distance, their existence betrayed by the glittering vegetation which clothed their slopes, rose a line of hills; and between them and the shore stretched a vast forest of luminous fungi--a gleaming jungle of fleshy growths. “I’m afraid you’re right, Garth,” said the professor somewhat ruefully, “yet that will not prevent me revealing my knowledge should we ever return.” “Do you think there is any game in the jungle there, Mervyn?” asked the baronet at this point. “Probably,” returned the scientist, “but I would not build upon it if I were you, lest you are disappointed. A run ashore will be acceptable to all of us, I expect?” “Rather!” replied Garth. “See, there’s a little bay into which we might run the vessel.” Already Silas had sighted the spot the inventor mentioned, and, putting the wheel over, he steered the submarine for the entrance.