Like a seal dragging itself clear of the water, the Bird of Freedom began the ascent of the glacial river. Under her weight, the ice creaked ominously.
Quite a hundred feet from the edge, and twenty feet above the sea level, the sleigh made its way, till its progress was stopped by a stretch of clear ice terminating at a ridge of large, smooth boulders extending from side to side of the ravine.
"We want an aeroplane to surmount this lot," observed Guy. "How is it these stones are found on the surface of the ice instead of at the bottom?"
Leslie did not know. He appealed to Ranworth.
"In time, by the process known as regelation, the boulders will sink through the solid ice," he explained. "What has happened fairly recently is that an avalanche has toppled these stones upon the ice. See, they have already sunk deeply into it. Nothing short of a powerful explosion would shift them. Put her on the runners for crossing this smooth patch, Leslie. We must find the most likely place to make an attempt to surmount the ridge."
Almost on the extreme right of the ravine, the line of boulders was lower than elsewhere, averaging four feet above the surrounding ice. Even four feet of rock seemed to be a formidable obstacle.
Here Ranworth brought the sleigh to a standstill by putting her keen-edged steel plate which served as a rudder hard over until it was at right angles to the two main runners.
"Let us see what is beyond before we tackle this business," he said.
Leaving Leslie in charge, the rest of the crew alighted, and, with considerable difficulty, for the cold seemed to cut through their fur clothing and make their limbs sluggish and almost devoid of feeling, surmounted the line of boulders. Beyond was a heap of small stones which had quite recently slipped from the cliffs above.
"Hurrah!" shouted Ranworth. "These stones are priceless to us. Set to and throw a lot of them over the ridge. In half an hour we can build up an incline sufficient to allow the decapods to get a grip."