As they proceeded their shadows grew longer and longer and the light and heat of the sun diminished until they traveled in a semi-twilight that was always cold.
Long since they had been forced to fashion warmer garments from the pelts of the beasts they had killed. Tanar and Ja wanted to turn back toward the southeast, for their strange homing instinct drew them in that direction toward their own country, but David asked them to accompany him yet a little further for his mind had evolved a strange and wonderful theory and he wished to press on yet a little further to obtain still stronger proof of its correctness.
When they slept they rested beside roaring fires and once, when they awoke, they were covered by a light mantle of a cold, white substance that frightened the Pellucidarians, but that David knew was snow. And the air was full of whirling particles and the wind bit those portions of their faces that were exposed, for now they wore fur caps and hoods and their hands were covered with warm mittens.
“We cannot go much further in this direction,” said Ja, “or we shall all perish.”
“Perhaps you are right,” said David. “You four turn back to the southeast and I will go yet a little further to the north and overtake you when I have satisfied myself that a thing that I believe is true.”
“No,” cried Tanar, “we shall remain together. Where you go we shall go.”
“Yes,” said Ja, “we shall not abandon you.”
“Just a little further north, then,” said David, “and I shall be ready to turn back with you,” and so they forged ahead over snow covered ground into the deepening gloom that filled the souls of the Pellucidarians with terror. But after a while the wind changed and blew from the south and the snow melted and the air became balmy again, and still further on the twilight slowly lifted and the light increased, though the midday sun of Pellucidar was now scarcely visible behind them.
“I cannot understand it,” said Ja. “Why should it become lighter again, although the sun is ever further away behind us?”
“I do not know,” said Tanar. “Ask David.”