But, gaze as he would, he could see nothing—nothing but light; subdued, soft, beautiful light. He knew the ray was passing steadily downward, for the mechanism was working with its accustomed regularity, but it revealed to him nothing at all. He could not understand it; his brain was dazed. He thought there might be something the matter with his eyesight. He got down from the ladder and hurriedly sent for Margaret, and when she came he begged her to look through the telescope and tell him what she saw. She went inside the screen, ascended the ladder, and looked down.

“It isn't anything,” she called out presently. “It looks like lighter air; it can't be that. Perhaps there is something the matter with your telescope.”

Clewe had thought of that, and as soon as she came out he examined the instrument, but the lenses were all right. There was nothing the matter with the telescope.

That night Roland Clewe spent in the lens-house, almost constantly at the telescope, but nothing did he see but a disk of soft, white light.

“The world can't be hollow!” he said to Margaret the next morning. “It can't be filled with air, or nothing, and my ray would not illuminate air or nothing. I cannot understand it. If you did not see what I see, I should think I was going crazy.”

“Don't talk that way,” exclaimed Margaret. “This may be some cavity which the ray will soon pass through, and then we shall come to the good old familiar rock again.”

But Clewe could not be consoled in this way. He could see no reason why his ray acting upon the emptiness of a cavern should produce the effect he beheld. Moreover, if the ray had revealed a cavern of considerable extent he could not expect that it could now pass through it, for the limit of its operations was almost reached. His electric cumulators would cease to act in a few hours more. The ray had now descended more than fourteen miles—its limit was fifteen.

Margaret was greatly troubled because of the effect of this result of the light borer upon Roland. His disappointment was very great, and it showed itself in his face. His Artesian ray had gone down to a distance greater than had been sometimes estimated as the thickness of the earth's crust, and the result was of no value. Roland did not believe that the earth had a crust. He had no faith in the old-fashioned idea that the great central portion was a mass of molten matter, but he could not drive from his mind the conviction that his light had passed through the solid portion of the earth, and had emerged into something which was not solid, which was not liquid, which was in fact nothing.

All his labors had come to this: he had discovered that the various strata near the earth's surface rested upon a vast bed of rock, and that this bed of rock rested upon nothing. Of course it was not impossible that the arrangement of the substances which make up this globe was peculiar at this point, and that there was a great cavern fourteen miles below him; but why should such a cavern be filled with a light different from that which would be shown by his Artesian ray when shining upon any other substances, open air or solid matter?

He could go no deeper down—at least at present. If he could make an instrument of increased power, it would require many months to do it.