It was not long after that, however, when even this daring boy's face sobered. Old Rover, who had been following the trail unhesitatingly, suddenly came to a halt. He turned to the right, sniffing the ice. Then he turned to the left. After that he looked up into the face of the boy, as if to say:
"Where's the trail gone?"
Phi examined the ice carefully.
"Been a sudden jam here," he muttered; "then the ice has slid along, some north, some south. It has all happened since our friends passed this way. You just wait here. I'll take Rover to the north and let him pick up the trail. When I find it, I'll come back far enough to call to you. May be to the south, though, but we'll soon see."
He disappeared around a giant ice-pile and, in a twinkling, was lost to view.
The two girls, placing their burdens of food and Marian's sketches on an up-ended ice-cake, sat down to wait. They were growing weary. The strain of the adventure into this puzzling, unknown ice-field was telling on their nerves.
"I wish we were safe at Cape Prince of Wales," sighed Marian.
"Yes, or even East Cape," said Lucile. "I think I'd be content to stay there and chance the year with the natives."
"Anyway, Phi's doing his best," said Marian. "Isn't he a strange one, though? Do you think he has the blue envelope?"
"I don't know."